Gk6RF5k3C2M.json

[
    {
        "text": "[MUSIC PLAYING]",
        "start": 0.0,
        "duration": 2.495
    },
    {
        "text": "SPEAKER 1: Hello and welcome\nfor Lecture 3 in React Native.",
        "start": 16.48,
        "duration": 3.844
    },
    {
        "text": "So previous lecture we talked\nabout a bunch of different topics;",
        "start": 20.324,
        "duration": 2.666
    },
    {
        "text": "one being classes and how ES6\nallows you to write classes.",
        "start": 22.99,
        "duration": 4.23
    },
    {
        "text": "React, we talked about\nthe library by Facebook",
        "start": 27.22,
        "duration": 2.73
    },
    {
        "text": "that allows you to write\ndeclarative programming.",
        "start": 29.95,
        "duration": 2.309
    },
    {
        "text": "We talked about what imperative\nand declarative programming were",
        "start": 32.259,
        "duration": 3.721
    },
    {
        "text": "and how React allows you\nto write declaratively.",
        "start": 35.98,
        "duration": 2.4
    },
    {
        "text": "We talked about props, which\nare basically an object that",
        "start": 38.38,
        "duration": 2.55
    },
    {
        "text": "are passed down to elements.",
        "start": 40.93,
        "duration": 1.71
    },
    {
        "text": "We talked about state, which is a\nmanagement system for allowing you",
        "start": 42.64,
        "duration": 6.09
    },
    {
        "text": "to track state in a class component.",
        "start": 48.73,
        "duration": 3.06
    },
    {
        "text": "We implemented the to do app in\nReact and then we teased at something",
        "start": 51.79,
        "duration": 3.57
    },
    {
        "text": "called React Native.",
        "start": 55.36,
        "duration": 1.71
    },
    {
        "text": "And so this lecture we'll be\ntalking a lot about React Native.",
        "start": 57.07,
        "duration": 2.73
    },
    {
        "text": "React Native is a framework\nthat relies on React Core.",
        "start": 59.8,
        "duration": 3.0
    },
    {
        "text": "And so a lot of the paradigms that apply\nto React also apply to React Native.",
        "start": 62.8,
        "duration": 4.79
    },
    {
        "text": "And it allows us to build mobile\napps using only JavaScript.",
        "start": 67.59,
        "duration": 3.76
    },
    {
        "text": "And so, as the React team like\nto say when this was released,",
        "start": 71.35,
        "duration": 4.14
    },
    {
        "text": "you can learn once and write everywhere.",
        "start": 75.49,
        "duration": 4.11
    },
    {
        "text": "And so React Native\nsupports iOS and Android,",
        "start": 79.6,
        "duration": 2.31
    },
    {
        "text": "and we'll see later today\nhow we get that going.",
        "start": 81.91,
        "duration": 4.62
    },
    {
        "text": "And so how exactly does this work?",
        "start": 86.53,
        "duration": 1.99
    },
    {
        "text": "How are we allowed to write JavaScript\nand have it run on mobile devices?",
        "start": 88.52,
        "duration": 4.85
    },
    {
        "text": "So first, the JavaScript is bundled.",
        "start": 93.37,
        "duration": 1.5
    },
    {
        "text": "So, just like in React, what happens\nare a couple of different steps",
        "start": 94.87,
        "duration": 4.17
    },
    {
        "text": "where your JavaScript is transpilaged\nso going from ES6, ES7, ES-next,",
        "start": 99.04,
        "duration": 5.61
    },
    {
        "text": "down to ES5 code, and\nit's also minified.",
        "start": 104.65,
        "duration": 3.65
    },
    {
        "text": "And so throughout the process you\ngo from a bunch of different files",
        "start": 108.3,
        "duration": 2.86
    },
    {
        "text": "all to one big JavaScript bundle.",
        "start": 111.16,
        "duration": 3.81
    },
    {
        "text": "This runs on your phone.",
        "start": 114.97,
        "duration": 1.327
    },
    {
        "text": "There are separate threads\nfor UI layout and JavaScript.",
        "start": 116.297,
        "duration": 2.333
    },
    {
        "text": "And so, as we saw, if we're\nrunning JavaScript in the browser",
        "start": 118.63,
        "duration": 2.73
    },
    {
        "text": "and that locks up, then nothing works.",
        "start": 121.36,
        "duration": 2.899
    },
    {
        "text": "But in React Native there\nare actually separate threads",
        "start": 124.259,
        "duration": 2.291
    },
    {
        "text": "for the UI layout and JavaScript.",
        "start": 126.55,
        "duration": 1.95
    },
    {
        "text": "And these different threads communicate\nasynchronously through a bridge.",
        "start": 131.95,
        "duration": 5.44
    },
    {
        "text": "And so the JavaScript\nthread will request",
        "start": 137.39,
        "duration": 2.18
    },
    {
        "text": "UI elements to be shown and\nthen, like I alluded to earlier,",
        "start": 139.57,
        "duration": 4.45
    },
    {
        "text": "the JavaScript thread can be\nblocked and the UI still works.",
        "start": 144.02,
        "duration": 2.92
    },
    {
        "text": "And so what do I mean by this bridge?",
        "start": 146.94,
        "duration": 3.86
    },
    {
        "text": "And so what ends up happening\nis there are separate threads.",
        "start": 150.8,
        "duration": 3.14
    },
    {
        "text": "So there's one thread for the UI and\nthere's one thread for JavaScript.",
        "start": 153.94,
        "duration": 5.275
    },
    {
        "text": "And so say we're writing React and\nwe have something like a button",
        "start": 162.54,
        "duration": 7.43
    },
    {
        "text": "that we want to be shown.",
        "start": 169.97,
        "duration": 1.97
    },
    {
        "text": "Basically what happens is\nthere's this bridge which will",
        "start": 171.94,
        "duration": 7.56
    },
    {
        "text": "communicate between these two threads.",
        "start": 179.5,
        "duration": 1.59
    },
    {
        "text": "And so the JavaScript\nwill basically say,",
        "start": 181.09,
        "duration": 2.11
    },
    {
        "text": "hey UI thread I want a view or a button.",
        "start": 183.2,
        "duration": 4.49
    },
    {
        "text": "And then UI will basically\nsay, OK here it is a button.",
        "start": 194.4,
        "duration": 4.197
    },
    {
        "text": "And then if I, as a\nuser, go ahead and press",
        "start": 198.597,
        "duration": 1.833
    },
    {
        "text": "that the UI will actually\nsend over to the JavaScript,",
        "start": 200.43,
        "duration": 4.427
    },
    {
        "text": "oh the button was pressed.",
        "start": 204.857,
        "duration": 1.083
    },
    {
        "text": "And so this bridge here\nis asynchronous, so",
        "start": 214.32,
        "duration": 2.64
    },
    {
        "text": "if something happens on the JavaScript\nand the JavaScript is actually",
        "start": 216.96,
        "duration": 2.94
    },
    {
        "text": "clogged and blocking, the UI\nthread can still do its thing",
        "start": 219.9,
        "duration": 3.18
    },
    {
        "text": "and I'll show you an\nexample of that in a second.",
        "start": 223.08,
        "duration": 2.62
    },
    {
        "text": "And, conversely, when you\ntouch something on the UI",
        "start": 225.7,
        "duration": 4.25
    },
    {
        "text": "the JavaScript doesn't know\nuntil the bridge basically says,",
        "start": 229.95,
        "duration": 3.73
    },
    {
        "text": "hey, this button was pressed and the\nUI can talk to the JavaScript that way.",
        "start": 233.68,
        "duration": 4.46
    },
    {
        "text": "And so let's see some example where\nwe can lock up that JavaScript thread",
        "start": 238.14,
        "duration": 4.83
    },
    {
        "text": "and not have the UI lock up.",
        "start": 242.97,
        "duration": 3.24
    },
    {
        "text": "And so here we are in\nthe Snack, snack.expo.io,",
        "start": 246.21,
        "duration": 5.49
    },
    {
        "text": "and this allows us to run React Native\nand have it all happen in the browser.",
        "start": 251.7,
        "duration": 4.92
    },
    {
        "text": "And so a few lectures ago we wrote this\nblocking method that basically locks up",
        "start": 256.62,
        "duration": 6.404
    },
    {
        "text": "the JavaScript thread.",
        "start": 263.024,
        "duration": 0.916
    },
    {
        "text": "So we can go ahead and do that again.",
        "start": 263.94,
        "duration": 1.61
    },
    {
        "text": "So say we have a method\ncalled block JavaScript.",
        "start": 265.55,
        "duration": 4.33
    },
    {
        "text": "And what that does is you can say, we're\ngoing to block and then do this thing,",
        "start": 269.88,
        "duration": 9.4
    },
    {
        "text": "so while date.now so we can say,\ncons done is five seconds from now.",
        "start": 279.28,
        "duration": 9.68
    },
    {
        "text": "And we can say, while it has not\nbeen that much time just do nothing.",
        "start": 293.9,
        "duration": 5.31
    },
    {
        "text": "And then when that's done\nwe can say, OK we're done.",
        "start": 302.904,
        "duration": 2.166
    },
    {
        "text": "And so down here, let's\nactually create a scroll view--",
        "start": 310.78,
        "duration": 3.07
    },
    {
        "text": "we'll see what that is in a second--",
        "start": 313.85,
        "duration": 1.5
    },
    {
        "text": "and a button.",
        "start": 320.239,
        "duration": 0.541
    },
    {
        "text": "And we actually don't care\nabout any of all that stuff.",
        "start": 328.999,
        "duration": 2.291
    },
    {
        "text": "And so, when this\nbutton is clicked, we're",
        "start": 341.691,
        "duration": 1.749
    },
    {
        "text": "going to go ahead and\nblock that JavaScript.",
        "start": 343.44,
        "duration": 1.9
    },
    {
        "text": "All right.",
        "start": 356.61,
        "duration": 0.98
    },
    {
        "text": "So everybody following?",
        "start": 361.52,
        "duration": 1.0
    },
    {
        "text": "So, so far we have a scroll view\nwhich is basically just a view that",
        "start": 362.52,
        "duration": 4.83
    },
    {
        "text": "can scroll back and forth.",
        "start": 367.35,
        "duration": 2.08
    },
    {
        "text": "We have a button that says block\nJavaScript, and when it's clicked,",
        "start": 369.43,
        "duration": 3.95
    },
    {
        "text": "it will run this function\nthat blocks the JavaScript.",
        "start": 373.38,
        "duration": 3.375
    },
    {
        "text": "And so watch what happens\nwhen I click this button.",
        "start": 376.755,
        "duration": 3.255
    },
    {
        "text": "Small bug.",
        "start": 391.24,
        "duration": 0.99
    },
    {
        "text": "All right here's a chance.",
        "start": 398.437,
        "duration": 1.083
    },
    {
        "text": "Who can spot the bug?",
        "start": 399.52,
        "duration": 0.874
    },
    {
        "text": "Oh, on press.",
        "start": 407.0,
        "duration": 2.71
    },
    {
        "text": "So on press, it will actually\nblock the JavaScript.",
        "start": 409.71,
        "duration": 2.46
    },
    {
        "text": "And you see how it still is scrolling,\nbut that button is locked up.",
        "start": 412.17,
        "duration": 4.26
    },
    {
        "text": "And then only after five seconds\nhave passed do the logs come through",
        "start": 416.43,
        "duration": 4.68
    },
    {
        "text": "and then the button returns\nto its normal state.",
        "start": 421.11,
        "duration": 3.15
    },
    {
        "text": "But notice how when it\nwas stuck and locked,",
        "start": 424.26,
        "duration": 2.302
    },
    {
        "text": "when the JavaScript thread\nwas locked, we still",
        "start": 426.562,
        "duration": 1.958
    },
    {
        "text": "had the ability to\nscroll back and forth.",
        "start": 428.52,
        "duration": 2.85
    },
    {
        "text": "That's because all of the JavaScript\nis controlled on one thread",
        "start": 431.37,
        "duration": 3.12
    },
    {
        "text": "whereas on the other thread all of the\nUI elements still worked as intended.",
        "start": 434.49,
        "duration": 4.9
    },
    {
        "text": "And so even though the JavaScript\nthread was locked up here,",
        "start": 439.39,
        "duration": 2.51
    },
    {
        "text": "it was in this while loop\ndoing nothing, the UI elements",
        "start": 441.9,
        "duration": 4.05
    },
    {
        "text": "were still able to\nscroll back and forth.",
        "start": 445.95,
        "duration": 2.86
    },
    {
        "text": "And so it's not as big\nof a deal if you lock up",
        "start": 448.81,
        "duration": 3.59
    },
    {
        "text": "the JavaScript thread in React\nNative but it's still a big deal",
        "start": 452.4,
        "duration": 3.45
    },
    {
        "text": "because none of your\nevent handlers will fire.",
        "start": 455.85,
        "duration": 3.87
    },
    {
        "text": "So any questions about how React Native\nworks, how these UI and JavaScript",
        "start": 462.75,
        "duration": 5.45
    },
    {
        "text": "threads run separately in the bridge?",
        "start": 468.2,
        "duration": 3.0
    },
    {
        "text": "Great.",
        "start": 471.2,
        "duration": 1.86
    },
    {
        "text": "And so what are some of the differences\nbetween React Native and React Web",
        "start": 473.06,
        "duration": 3.15
    },
    {
        "text": "which we've been talking about thus far?",
        "start": 476.21,
        "duration": 2.157
    },
    {
        "text": "So there are differences\nin base components.",
        "start": 478.367,
        "duration": 1.833
    },
    {
        "text": "So as you saw in my quick example,\nthings like scroll view or capital",
        "start": 480.2,
        "duration": 3.63
    },
    {
        "text": "button do not exist in web.",
        "start": 483.83,
        "duration": 2.205
    },
    {
        "text": "Things like style, the way\nthat you style elements,",
        "start": 486.035,
        "duration": 2.125
    },
    {
        "text": "is slightly different in React\nNative and you don't actually",
        "start": 488.16,
        "duration": 3.23
    },
    {
        "text": "have browser APIs anymore.",
        "start": 491.39,
        "duration": 2.79
    },
    {
        "text": "So things like CSS, animations,\ncanvas, SVG, things like that",
        "start": 494.18,
        "duration": 4.17
    },
    {
        "text": "don't actually exist in React Native.",
        "start": 498.35,
        "duration": 2.467
    },
    {
        "text": "But there are actually things\nthat have been polyfilled.",
        "start": 500.817,
        "duration": 2.333
    },
    {
        "text": "So polyfilled is a term that people use\nto mean some methods or functions that",
        "start": 503.15,
        "duration": 6.9
    },
    {
        "text": "might exist in one environment do not\nnecessarily exist in all environments.",
        "start": 510.05,
        "duration": 3.97
    },
    {
        "text": "And by polyfilling these we can\nactually implement them such",
        "start": 514.02,
        "duration": 3.92
    },
    {
        "text": "that all environments\nwill actually have these.",
        "start": 517.94,
        "duration": 2.03
    },
    {
        "text": "And so fetch is something that's\nnot supported by all browsers,",
        "start": 519.97,
        "duration": 4.199
    },
    {
        "text": "but by polyfilling it\nyou can actually include",
        "start": 524.169,
        "duration": 2.891
    },
    {
        "text": "code that will implement fetch\nif it doesn't exist already.",
        "start": 527.06,
        "duration": 2.88
    },
    {
        "text": "And so things like fetch timers like\nset interval or console or console.log,",
        "start": 529.94,
        "duration": 6.24
    },
    {
        "text": "console.warn, and stuff like\nthat have been polyfilled so",
        "start": 536.18,
        "duration": 3.995
    },
    {
        "text": "that they work in React Native as well.",
        "start": 540.175,
        "duration": 4.144
    },
    {
        "text": "And also the way that\nyou handle navigation",
        "start": 544.319,
        "duration": 1.791
    },
    {
        "text": "is slightly different in\nReact Native, and we'll",
        "start": 546.11,
        "duration": 1.999
    },
    {
        "text": "talk about that in a future lecture.",
        "start": 548.109,
        "duration": 1.993
    },
    {
        "text": "And so I said that React Native base\ncomponents are slightly different.",
        "start": 550.102,
        "duration": 2.958
    },
    {
        "text": "And so what do I mean there?",
        "start": 553.06,
        "duration": 2.81
    },
    {
        "text": "So in React Web we had access to\nthings like div or span or P image,",
        "start": 555.87,
        "duration": 4.82
    },
    {
        "text": "and we can just declare those globally.",
        "start": 560.69,
        "duration": 2.84
    },
    {
        "text": "But in React Native we actually have to\nimport from the React Native library,",
        "start": 563.53,
        "duration": 4.6
    },
    {
        "text": "and we'll see how to do\nthat in a little bit.",
        "start": 568.13,
        "duration": 2.64
    },
    {
        "text": "And so divs no longer exist and\nwhat we use instead are Views.",
        "start": 570.77,
        "duration": 2.84
    },
    {
        "text": "So View with a capital V is basically\na cross-platform, just blank E-Y slate.",
        "start": 573.61,
        "duration": 7.58
    },
    {
        "text": "So basically the same thing as a div.",
        "start": 581.19,
        "duration": 3.17
    },
    {
        "text": "There's no such thing\nas span or P anymore",
        "start": 584.36,
        "duration": 2.31
    },
    {
        "text": "and so instead we use this text.",
        "start": 586.67,
        "duration": 1.887
    },
    {
        "text": "And so what's unique in React\nNative is that all text actually",
        "start": 588.557,
        "duration": 2.583
    },
    {
        "text": "must be wrapped by this text tag.",
        "start": 591.14,
        "duration": 3.69
    },
    {
        "text": "As you saw in this previous\nexample lower case button",
        "start": 594.83,
        "duration": 2.52
    },
    {
        "text": "doesn't exist anymore.",
        "start": 597.35,
        "duration": 1.45
    },
    {
        "text": "Instead, we use capitol Button\nwith a slightly different API.",
        "start": 598.8,
        "duration": 2.81
    },
    {
        "text": "And so from React Web, if you\nwant to attach a handler to that",
        "start": 601.61,
        "duration": 3.66
    },
    {
        "text": "you do on click.",
        "start": 605.27,
        "duration": 1.2
    },
    {
        "text": "Whereas, in React Native, you\ndo on press which was actually",
        "start": 606.47,
        "duration": 3.78
    },
    {
        "text": "the bug in the code earlier.",
        "start": 610.25,
        "duration": 2.85
    },
    {
        "text": "And lastly we have these things\ncalled scroll views or lists which",
        "start": 613.1,
        "duration": 3.87
    },
    {
        "text": "don't really exist in web world, but\nthey do exist a lot in React Native,",
        "start": 616.97,
        "duration": 5.82
    },
    {
        "text": "and we'll be talking about\nthose in the future as well.",
        "start": 622.79,
        "duration": 2.852
    },
    {
        "text": "Of course there are many,\nmany other components",
        "start": 625.642,
        "duration": 1.958
    },
    {
        "text": "and, if you want to explore them,\nthe documentation is really good.",
        "start": 627.6,
        "duration": 3.84
    },
    {
        "text": "Cool, so let's actually\ntake that example",
        "start": 634.52,
        "duration": 2.04
    },
    {
        "text": "that we wrote last lecture,\nthe to do app, and actually",
        "start": 636.56,
        "duration": 3.36
    },
    {
        "text": "translate it into React Native.",
        "start": 639.92,
        "duration": 2.12
    },
    {
        "text": "And so I have here this implementation,\nwhich is exactly the code",
        "start": 642.04,
        "duration": 6.82
    },
    {
        "text": "that we wrote in the previous lecture.",
        "start": 648.86,
        "duration": 1.624
    },
    {
        "text": "And what we're going to do is\ncopy and paste that into the Snack",
        "start": 650.484,
        "duration": 2.666
    },
    {
        "text": "that we saw earlier and go ahead and\ntranslate that into React Native.",
        "start": 653.15,
        "duration": 3.18
    },
    {
        "text": "So this is just the command\nto copy it and let's actually",
        "start": 661.67,
        "duration": 4.74
    },
    {
        "text": "paste that into here.",
        "start": 666.41,
        "duration": 3.15
    },
    {
        "text": "So of course there's going to be many\nerrors just because this is React Web",
        "start": 669.56,
        "duration": 3.27
    },
    {
        "text": "and we're trying to run\nthis in React Native.",
        "start": 672.83,
        "duration": 2.22
    },
    {
        "text": "And so let's go ahead and\ntry to fix those errors.",
        "start": 675.05,
        "duration": 3.27
    },
    {
        "text": "And so first we see stuff like\nLI, input, button, and those",
        "start": 678.32,
        "duration": 4.71
    },
    {
        "text": "don't exist in React Native.",
        "start": 683.03,
        "duration": 1.32
    },
    {
        "text": "And so we'll have to first\nreplace those React Web",
        "start": 684.35,
        "duration": 3.45
    },
    {
        "text": "components with React Native ones.",
        "start": 687.8,
        "duration": 3.85
    },
    {
        "text": "And so this rendering\ndoes not exist anymore.",
        "start": 691.65,
        "duration": 2.255
    },
    {
        "text": "And so let's first do import\nsome stuff from React Native.",
        "start": 693.905,
        "duration": 6.375
    },
    {
        "text": "And we'll be talking about imports\nand exports a little bit later,",
        "start": 700.28,
        "duration": 3.82
    },
    {
        "text": "but just bear with me for now.",
        "start": 704.1,
        "duration": 1.73
    },
    {
        "text": "And so some things that we're\ngoing to need are stuff like View,",
        "start": 705.83,
        "duration": 3.16
    },
    {
        "text": "we'll need a Button and we'll need text.",
        "start": 708.99,
        "duration": 2.72
    },
    {
        "text": "And we'll need some scrolling\nviews and then maybe",
        "start": 715.88,
        "duration": 4.71
    },
    {
        "text": "some more stuff in a little bit.",
        "start": 720.59,
        "duration": 2.07
    },
    {
        "text": "So first let's work on\nthat quick to do component.",
        "start": 722.66,
        "duration": 3.36
    },
    {
        "text": "And so we have a list item here,\ninstead let's actually use a View.",
        "start": 726.02,
        "duration": 3.15
    },
    {
        "text": "Let's actually get rid of this input for\nnow, and we'll add that in a little bit",
        "start": 734.2,
        "duration": 4.35
    },
    {
        "text": "later.",
        "start": 738.55,
        "duration": 1.05
    },
    {
        "text": "But how are we going to change this\nlowercase button to React Native?",
        "start": 739.6,
        "duration": 4.336
    },
    {
        "text": "Well first we need to replace it\nwith the capital Button, which",
        "start": 743.936,
        "duration": 2.624
    },
    {
        "text": "is React Natives version of the button.",
        "start": 746.56,
        "duration": 2.174
    },
    {
        "text": "It no longer has an on click\nproperty and so instead we'll",
        "start": 748.734,
        "duration": 2.416
    },
    {
        "text": "pass an on press prop and then we don't\nactually wrap the content any more",
        "start": 751.15,
        "duration": 6.69
    },
    {
        "text": "instead we pass a title prop.",
        "start": 757.84,
        "duration": 2.48
    },
    {
        "text": "And so that button's done.",
        "start": 763.026,
        "duration": 1.874
    },
    {
        "text": "What are we going to do for span?",
        "start": 764.9,
        "duration": 1.73
    },
    {
        "text": "Anyone?",
        "start": 766.63,
        "duration": 1.536
    },
    {
        "text": "AUDIENCE: [INAUDIBLE]",
        "start": 768.166,
        "duration": 0.874
    },
    {
        "text": "SPEAKER 1: Yeah, we'll\nuse a text instead.",
        "start": 769.04,
        "duration": 1.749
    },
    {
        "text": "And now our to do is done.",
        "start": 773.41,
        "duration": 2.73
    },
    {
        "text": "So now let's start looking\ninto this app component.",
        "start": 776.14,
        "duration": 3.201
    },
    {
        "text": "So first let's get rid of this render,\nwhich does not exist in React Native,",
        "start": 782.17,
        "duration": 5.94
    },
    {
        "text": "and let's start working our way\nthrough this big return function here.",
        "start": 788.11,
        "duration": 3.48
    },
    {
        "text": "So first we have a div.",
        "start": 791.59,
        "duration": 1.23
    },
    {
        "text": "Instead of a div let's\ngo ahead and use a View.",
        "start": 792.82,
        "duration": 2.25
    },
    {
        "text": "And then we have a to do count.",
        "start": 798.639,
        "duration": 1.291
    },
    {
        "text": "So what are we going to\nuse instead of this div?",
        "start": 799.93,
        "duration": 3.27
    },
    {
        "text": "We can't use a View\notherwise an error will",
        "start": 803.2,
        "duration": 1.86
    },
    {
        "text": "be thrown because remember the\nonly way that we can include text",
        "start": 805.06,
        "duration": 3.63
    },
    {
        "text": "in React Native is by wrapping it in\nthis text component and same thing",
        "start": 808.69,
        "duration": 5.921
    },
    {
        "text": "with this.",
        "start": 814.611,
        "duration": 0.499
    },
    {
        "text": "All right, we see another button\nand we've seen a button before,",
        "start": 817.924,
        "duration": 2.666
    },
    {
        "text": "so all we have to do is replace\nthat lowercase b with a capital B,",
        "start": 820.59,
        "duration": 3.5
    },
    {
        "text": "change on click to on press and\nchange the content to be title.",
        "start": 824.09,
        "duration": 4.495
    },
    {
        "text": "And then we're done there.",
        "start": 835.007,
        "duration": 1.083
    },
    {
        "text": "All right, UL, unordered lists.",
        "start": 841.39,
        "duration": 2.29
    },
    {
        "text": "So how might we handle this\nunordered list in React Native?",
        "start": 843.68,
        "duration": 5.35
    },
    {
        "text": "So lists, ULs and ordered\nlists don't actually",
        "start": 849.03,
        "duration": 4.15
    },
    {
        "text": "exist in React Native, and the\nway that we handled those instead",
        "start": 853.18,
        "duration": 2.89
    },
    {
        "text": "are by using the scrolling\ncomponents because we don't know",
        "start": 856.07,
        "duration": 6.815
    },
    {
        "text": "how long that list is going\nto get and so we better",
        "start": 862.885,
        "duration": 2.125
    },
    {
        "text": "assume it's going to get pretty long\nand be able to scroll through them",
        "start": 865.01,
        "duration": 2.07
    },
    {
        "text": "if we needed.",
        "start": 867.08,
        "duration": 1.31
    },
    {
        "text": "And so unordered lists we\nreplace with scroll view",
        "start": 868.39,
        "duration": 4.18
    },
    {
        "text": "and now we have what\nwe were looking for.",
        "start": 872.57,
        "duration": 3.01
    },
    {
        "text": "So all of the React Native components,\nthe React components sorry,",
        "start": 875.58,
        "duration": 3.88
    },
    {
        "text": "we've changed to React Native\ncomponents and now we have--",
        "start": 879.46,
        "duration": 3.388
    },
    {
        "text": "Oops, something's breaking still.",
        "start": 882.848,
        "duration": 2.322
    },
    {
        "text": "Prompt is another one\nof those browser APIs",
        "start": 890.42,
        "duration": 3.9
    },
    {
        "text": "that just does not exist in\nthe React Native world which",
        "start": 894.32,
        "duration": 2.7
    },
    {
        "text": "caused our code to crash.",
        "start": 897.02,
        "duration": 1.39
    },
    {
        "text": "And so rather than using\none of these browser",
        "start": 898.41,
        "duration": 2.96
    },
    {
        "text": "APIs let's just replace it with\nsome hard coded text for now,",
        "start": 901.37,
        "duration": 3.21
    },
    {
        "text": "maybe something like to do, number,\nand then whatever it's ID is.",
        "start": 904.58,
        "duration": 8.15
    },
    {
        "text": "And rather than\nincrementing ID down there",
        "start": 916.511,
        "duration": 1.749
    },
    {
        "text": "let's actually increment it up here.",
        "start": 918.26,
        "duration": 1.5
    },
    {
        "text": "And so now it works.",
        "start": 922.51,
        "duration": 1.15
    },
    {
        "text": "So we have to do number\none, to do number two",
        "start": 923.66,
        "duration": 2.42
    },
    {
        "text": "and you can see how we add those.",
        "start": 926.08,
        "duration": 3.31
    },
    {
        "text": "And so we'll fix the\nstyle in the future,",
        "start": 929.39,
        "duration": 2.1
    },
    {
        "text": "but basically does\nanybody have questions",
        "start": 931.49,
        "duration": 2.64
    },
    {
        "text": "on going from React Web to React Native?",
        "start": 934.13,
        "duration": 3.39
    },
    {
        "text": "What we did there was just replace\nall the React Web components",
        "start": 937.52,
        "duration": 3.36
    },
    {
        "text": "with the React Native components.",
        "start": 940.88,
        "duration": 1.89
    },
    {
        "text": "And it is almost as easy as command\neffing and replacing like that.",
        "start": 942.77,
        "duration": 4.52
    },
    {
        "text": "Great.",
        "start": 951.291,
        "duration": 0.499
    },
    {
        "text": "And so how are you going to go\nabout styling those components?",
        "start": 951.79,
        "duration": 3.27
    },
    {
        "text": "So in React Web the way\nwe did that was just",
        "start": 955.06,
        "duration": 2.9
    },
    {
        "text": "by adding a class name and then\nstyling in CSS, but in React Native",
        "start": 957.96,
        "duration": 3.89
    },
    {
        "text": "we don't have this concept of CSS.",
        "start": 961.85,
        "duration": 3.492
    },
    {
        "text": "So the way that React\nNative handles that",
        "start": 965.342,
        "duration": 1.708
    },
    {
        "text": "is by actually using JavaScript objects\nfor styling and what that gives us",
        "start": 967.05,
        "duration": 3.33
    },
    {
        "text": "is the ability to use dynamic styles.",
        "start": 970.38,
        "duration": 4.11
    },
    {
        "text": "Object keys in these objects\nare based on CSS properties,",
        "start": 974.49,
        "duration": 3.35
    },
    {
        "text": "so we have stuff like margin top,\nmargin bottom, margin padding.",
        "start": 977.84,
        "duration": 5.726
    },
    {
        "text": "And the layout system\nthat we used is Flexbox",
        "start": 983.566,
        "duration": 1.874
    },
    {
        "text": "and so, if you're familiar\nwith the Flexbox system in web,",
        "start": 985.44,
        "duration": 2.416
    },
    {
        "text": "it's almost exactly the\nsame in React Native.",
        "start": 987.856,
        "duration": 3.104
    },
    {
        "text": "One of the key differences\nis that rather than",
        "start": 990.96,
        "duration": 3.06
    },
    {
        "text": "defaulting to row we default to\nlaying out things in columns.",
        "start": 994.02,
        "duration": 7.48
    },
    {
        "text": "So, in React Web, we have this\nconcept of pixels or percentages,",
        "start": 1001.5,
        "duration": 3.52
    },
    {
        "text": "but in React Native we actually\nuse unit-less numbers for length.",
        "start": 1005.02,
        "duration": 4.36
    },
    {
        "text": "Which is good because there\nare so many different devices",
        "start": 1009.38,
        "duration": 3.48
    },
    {
        "text": "that this runs on with\ndifferent pixel densities",
        "start": 1012.86,
        "duration": 2.19
    },
    {
        "text": "that having a unit-less number allows\nus to abstract that pixel density out.",
        "start": 1015.05,
        "duration": 4.18
    },
    {
        "text": "The style prop, so the way that\nyou style a given component",
        "start": 1022.52,
        "duration": 3.72
    },
    {
        "text": "is by assigning that JavaScript\nobject to a style prop",
        "start": 1026.24,
        "duration": 3.89
    },
    {
        "text": "and it can actually\ntake an array of styles.",
        "start": 1030.13,
        "duration": 1.87
    },
    {
        "text": "And so, if you wanted to have a bunch\nof different class names in React Web",
        "start": 1032.0,
        "duration": 3.78
    },
    {
        "text": "you'd just start adding those\nwith a space in between.",
        "start": 1035.78,
        "duration": 3.6
    },
    {
        "text": "But in React Native you handled\nthat by passing an array of styles.",
        "start": 1039.38,
        "duration": 3.075
    },
    {
        "text": "So let's go ahead and add styles\nto this app that we have here.",
        "start": 1045.109,
        "duration": 7.121
    },
    {
        "text": "So first, let's go ahead\nand style this view.",
        "start": 1052.23,
        "duration": 2.24
    },
    {
        "text": "And so right now, as you see, each\nto do has a Delete button and a",
        "start": 1054.47,
        "duration": 6.27
    },
    {
        "text": "to do right under it, whereas in web\nwe had the Delete button next to that",
        "start": 1060.74,
        "duration": 4.24
    },
    {
        "text": "to do.",
        "start": 1064.98,
        "duration": 0.5
    },
    {
        "text": "And so let's try to\nfigure out exactly how we",
        "start": 1065.48,
        "duration": 2.32
    },
    {
        "text": "can get that Delete button over\nhere and the to do to be next to it.",
        "start": 1067.8,
        "duration": 4.7
    },
    {
        "text": "And so does anybody have any ideas\nabout how we might want to do that?",
        "start": 1072.5,
        "duration": 4.59
    },
    {
        "text": "We know we're going to\nhave to pass a style prop,",
        "start": 1077.09,
        "duration": 2.43
    },
    {
        "text": "and we know that it's\ngoing to be an object.",
        "start": 1079.52,
        "duration": 3.45
    },
    {
        "text": "And so this looks weird to\nhave those double curlies",
        "start": 1082.97,
        "duration": 2.46
    },
    {
        "text": "but the outer curlies\nmean, hey here comes",
        "start": 1085.43,
        "duration": 2.7
    },
    {
        "text": "some JavaScript and the inner\ncurlies are just an object",
        "start": 1088.13,
        "duration": 3.06
    },
    {
        "text": "literal like we've seen before.",
        "start": 1091.19,
        "duration": 2.88
    },
    {
        "text": "And so how might we get\nthose to dos to be in a row?",
        "start": 1094.07,
        "duration": 3.61
    },
    {
        "text": "So we saw before that React Native uses\nFlexbox in order to handle it's layout.",
        "start": 1100.35,
        "duration": 6.81
    },
    {
        "text": "And so we can just say, hey we want\nthe flex direction, rather than being",
        "start": 1107.16,
        "duration": 6.63
    },
    {
        "text": "column by default, let's set it to row.",
        "start": 1113.79,
        "duration": 2.818
    },
    {
        "text": "And so now we have the Delete\nbutton next to the to do.",
        "start": 1119.42,
        "duration": 5.19
    },
    {
        "text": "But it's annoying me a little bit how\nthat button is slightly below the text.",
        "start": 1124.61,
        "duration": 5.77
    },
    {
        "text": "And so how might we get those\nitems to be aligned to center?",
        "start": 1130.38,
        "duration": 5.36
    },
    {
        "text": "Well in Flexbox we have this\nthing called align items",
        "start": 1135.74,
        "duration": 6.12
    },
    {
        "text": "and then you just say, hey\nalign those to be center.",
        "start": 1141.86,
        "duration": 3.66
    },
    {
        "text": "Then all of a sudden we\nhave it aligned center.",
        "start": 1145.52,
        "duration": 2.27
    },
    {
        "text": "And just confirming that\ndelete button does indeed work.",
        "start": 1151.55,
        "duration": 3.841
    },
    {
        "text": "Great.",
        "start": 1155.391,
        "duration": 0.499
    },
    {
        "text": "Anybody notice any other\nbad style bugs over here?",
        "start": 1155.89,
        "duration": 3.45
    },
    {
        "text": "So look at this.",
        "start": 1161.89,
        "duration": 3.25
    },
    {
        "text": "So most phones will have some\nnav bar, and that nav bar",
        "start": 1165.14,
        "duration": 5.72
    },
    {
        "text": "will have stuff like if you're\nconnected to Wi-Fi, the time and etc.",
        "start": 1170.86,
        "duration": 3.87
    },
    {
        "text": "But that first view is actually\ngoing all the way to the top.",
        "start": 1174.73,
        "duration": 3.95
    },
    {
        "text": "And so how might we get all this\ncontent to be slightly moved down?",
        "start": 1178.68,
        "duration": 3.46
    },
    {
        "text": "So how would we do that in Web?",
        "start": 1186.29,
        "duration": 2.75
    },
    {
        "text": "AUDIENCE: Add a margin.",
        "start": 1189.04,
        "duration": 1.98
    },
    {
        "text": "SPEAKER 1: Yeah we would add a\nmargin or some padding or something",
        "start": 1191.02,
        "duration": 2.75
    },
    {
        "text": "to move the content from\nthe top slightly down.",
        "start": 1193.77,
        "duration": 4.09
    },
    {
        "text": "And so we could do that\nin React Native as well.",
        "start": 1197.86,
        "duration": 3.68
    },
    {
        "text": "So you can say with this view, let's\nactually put a padding on the top",
        "start": 1201.54,
        "duration": 7.57
    },
    {
        "text": "and let's just say something like\n50 which is somewhat arbitrary.",
        "start": 1209.11,
        "duration": 4.741
    },
    {
        "text": "And now we've gone ahead and\nmoved that down slightly.",
        "start": 1213.851,
        "duration": 2.249
    },
    {
        "text": "But what if we wanted to move it down\nexactly the same amount as the status",
        "start": 1219.46,
        "duration": 6.08
    },
    {
        "text": "bar?",
        "start": 1225.54,
        "duration": 0.5
    },
    {
        "text": "Well there's this great\ntool called Expo which",
        "start": 1228.96,
        "duration": 2.85
    },
    {
        "text": "we'll talk about in length later today.",
        "start": 1231.81,
        "duration": 1.84
    },
    {
        "text": "They're also the people\nwho designed Snack.",
        "start": 1233.65,
        "duration": 2.3
    },
    {
        "text": "And they actually give you\nthis thing called constant",
        "start": 1235.95,
        "duration": 2.61
    },
    {
        "text": "so we can do import constants from Expo.",
        "start": 1238.56,
        "duration": 3.515
    },
    {
        "text": "And we can actually say,\nhey padding top rather",
        "start": 1245.56,
        "duration": 2.2
    },
    {
        "text": "than assigning an arbitrary value of\n50 let's do constants.statusbarheight",
        "start": 1247.76,
        "duration": 8.76
    },
    {
        "text": "and that will actually give you\nthat exact status bar height",
        "start": 1256.52,
        "duration": 4.05
    },
    {
        "text": "even if you're on different phones.",
        "start": 1260.57,
        "duration": 2.174
    },
    {
        "text": "And so, again, we'll\ntalk about Expo and we'll",
        "start": 1262.744,
        "duration": 1.916
    },
    {
        "text": "talk about importing and\nexporting later today.",
        "start": 1264.66,
        "duration": 3.17
    },
    {
        "text": "But just FYI there's this thing called\nconstants.statusbarheight which will",
        "start": 1267.83,
        "duration": 3.99
    },
    {
        "text": "give us exactly that status bar height.",
        "start": 1271.82,
        "duration": 2.67
    },
    {
        "text": "And now we have a to do app\nthat doesn't look half bad.",
        "start": 1274.49,
        "duration": 3.14
    },
    {
        "text": "Cool.",
        "start": 1277.63,
        "duration": 0.5
    },
    {
        "text": "So there's actually this\nthing called style sheet",
        "start": 1278.13,
        "duration": 2.27
    },
    {
        "text": "which is part of React Native which has\nsome optimizations for these styles.",
        "start": 1280.4,
        "duration": 5.91
    },
    {
        "text": "And so we talked about earlier how the\nway that your JavaScript communicates",
        "start": 1286.31,
        "duration": 4.11
    },
    {
        "text": "with the UI throughout\nis through this bridge.",
        "start": 1290.42,
        "duration": 3.65
    },
    {
        "text": "And so that means every single\ntime you want a view with the style",
        "start": 1294.07,
        "duration": 3.46
    },
    {
        "text": "you need to send those style\nattributes over the bridge.",
        "start": 1297.53,
        "duration": 2.7
    },
    {
        "text": "There's actually a way\nthat you can optimize this.",
        "start": 1300.23,
        "duration": 2.13
    },
    {
        "text": "And so the Facebook team\ncreated this thing called",
        "start": 1302.36,
        "duration": 2.083
    },
    {
        "text": "style sheet which does this for you.",
        "start": 1304.443,
        "duration": 1.967
    },
    {
        "text": "So it's basically the same thing\nas creating objects for style,",
        "start": 1306.41,
        "duration": 2.67
    },
    {
        "text": "but as an additional optimization that\nrather than sending this style object",
        "start": 1309.08,
        "duration": 5.04
    },
    {
        "text": "over the bridge we can only send IDs.",
        "start": 1314.12,
        "duration": 2.55
    },
    {
        "text": "And so say we have these objects,\nrather than passing the full object",
        "start": 1316.67,
        "duration": 6.78
    },
    {
        "text": "every time you can just\nsay, hey this object,",
        "start": 1323.45,
        "duration": 1.925
    },
    {
        "text": "let's assign it this\narbitrary ID of one.",
        "start": 1325.375,
        "duration": 2.215
    },
    {
        "text": "And so every time we say, hey\nthis should have a style of one,",
        "start": 1327.59,
        "duration": 4.72
    },
    {
        "text": "the UI thread will know, oh, I\nknow exactly what style that means.",
        "start": 1332.31,
        "duration": 4.11
    },
    {
        "text": "And so to do that, all we have to do\nis import this thing called style sheet",
        "start": 1336.42,
        "duration": 6.26
    },
    {
        "text": "from React Native and we can do this.",
        "start": 1342.68,
        "duration": 1.77
    },
    {
        "text": "And so we're saying we're declaring our\nstyles as a constant outside of our app",
        "start": 1351.83,
        "duration": 5.42
    },
    {
        "text": "and we're saying, hey\ncreate this style sheet",
        "start": 1357.25,
        "duration": 2.64
    },
    {
        "text": "and we're going to pass into\nyou an object where the keys map",
        "start": 1359.89,
        "duration": 2.55
    },
    {
        "text": "with how we're going to use this later.",
        "start": 1362.44,
        "duration": 3.676
    },
    {
        "text": "And so we can go ahead\nand abstract this out.",
        "start": 1366.116,
        "duration": 1.874
    },
    {
        "text": "And so we can say, this\nhere we're actually",
        "start": 1367.99,
        "duration": 4.38
    },
    {
        "text": "going to call our to do container.",
        "start": 1372.37,
        "duration": 3.995
    },
    {
        "text": "And our to do container will just say,\nall right flex in the row direction",
        "start": 1380.085,
        "duration": 7.165
    },
    {
        "text": "and align your items to be centered.",
        "start": 1387.25,
        "duration": 2.922
    },
    {
        "text": "And then down here\nfor style we just say,",
        "start": 1390.172,
        "duration": 1.708
    },
    {
        "text": "oh, we want to use styles.todocontainer.",
        "start": 1391.88,
        "duration": 1.73
    },
    {
        "text": "And let's actually lowercase\nthis for convention.",
        "start": 1397.42,
        "duration": 5.04
    },
    {
        "text": "And as you can see those\nstyles still get applied.",
        "start": 1402.46,
        "duration": 3.86
    },
    {
        "text": "And why else might this pattern be good?",
        "start": 1406.32,
        "duration": 3.34
    },
    {
        "text": "Does anybody see something\nbetter about this pattern?",
        "start": 1409.66,
        "duration": 2.37
    },
    {
        "text": "AUDIENCE: It's reusable.",
        "start": 1415.229,
        "duration": 1.831
    },
    {
        "text": "SPEAKER 1: Yeah exactly, it's reusable.",
        "start": 1417.06,
        "duration": 3.21
    },
    {
        "text": "And so say we wanted to\nhave something else that",
        "start": 1420.27,
        "duration": 2.94
    },
    {
        "text": "had very similar styles\nto to do container",
        "start": 1423.21,
        "duration": 5.49
    },
    {
        "text": "we can actually use that again.",
        "start": 1428.7,
        "duration": 1.299
    },
    {
        "text": "And then if we wanted to change\nboth of them at the same time",
        "start": 1429.999,
        "duration": 2.541
    },
    {
        "text": "we could do it by using\nthis abstracted out object.",
        "start": 1432.54,
        "duration": 2.94
    },
    {
        "text": "And so let's do the app container\nand set that equal to this object.",
        "start": 1435.48,
        "duration": 7.66
    },
    {
        "text": "And then down here for this view\nlet's do styles.appcontainer.",
        "start": 1451.27,
        "duration": 3.75
    },
    {
        "text": "And so there's actually an\neven better reason to do this",
        "start": 1458.61,
        "duration": 4.99
    },
    {
        "text": "and it's because every\nsingle time we rendered,",
        "start": 1463.6,
        "duration": 2.29
    },
    {
        "text": "we used to be building a\nnew style object to pass.",
        "start": 1465.89,
        "duration": 2.87
    },
    {
        "text": "And now we're just using\nthat same reference",
        "start": 1468.76,
        "duration": 2.13
    },
    {
        "text": "to that object that we created\noutside of this component.",
        "start": 1470.89,
        "duration": 3.81
    },
    {
        "text": "And so that's just an additional\noptimization that, using this pattern,",
        "start": 1474.7,
        "duration": 4.99
    },
    {
        "text": "creating the styles outside of\nthe component allows us to do.",
        "start": 1479.69,
        "duration": 3.14
    },
    {
        "text": "Cool.",
        "start": 1485.56,
        "duration": 2.19
    },
    {
        "text": "Any questions on styles and styling?",
        "start": 1487.75,
        "duration": 3.68
    },
    {
        "text": "Great.",
        "start": 1491.43,
        "duration": 0.5
    },
    {
        "text": "So let's talk about event handling.",
        "start": 1494.69,
        "duration": 2.53
    },
    {
        "text": "So unlike Web not every component\nhas every single interaction.",
        "start": 1497.22,
        "duration": 3.71
    },
    {
        "text": "And so in Web, if we had a div, we\ncan assign an onClick to that div",
        "start": 1500.93,
        "duration": 3.24
    },
    {
        "text": "or if we add a list item or a list,\nanything we can assign an onClick to.",
        "start": 1504.17,
        "duration": 4.23
    },
    {
        "text": "But unlike Web there are only a few\ntouchable components in React Native",
        "start": 1508.4,
        "duration": 3.48
    },
    {
        "text": "and those are a button,\nwhich we've used before.",
        "start": 1511.88,
        "duration": 3.469
    },
    {
        "text": "These three things called touchable\nopacity, touchable highlight",
        "start": 1515.349,
        "duration": 2.666
    },
    {
        "text": "and touchable without\nfeedback, which are just",
        "start": 1518.015,
        "duration": 4.436
    },
    {
        "text": "three basic components that have\nslightly different reactions when",
        "start": 1522.451,
        "duration": 2.749
    },
    {
        "text": "you touch them.",
        "start": 1525.2,
        "duration": 1.292
    },
    {
        "text": "An then lastly, this thing\ncalled touchable native feedback",
        "start": 1526.492,
        "duration": 2.458
    },
    {
        "text": "which is this native component\nthat you can only use on Android.",
        "start": 1528.95,
        "duration": 4.09
    },
    {
        "text": "And so in Web, when you\nhad an event handler,",
        "start": 1536.33,
        "duration": 3.36
    },
    {
        "text": "that handler would receive\nthat event as an argument.",
        "start": 1539.69,
        "duration": 2.87
    },
    {
        "text": "But that's not necessarily true\nfor all React Native handlers.",
        "start": 1542.56,
        "duration": 5.88
    },
    {
        "text": "And so in order just to\nfind out how those work",
        "start": 1548.44,
        "duration": 2.57
    },
    {
        "text": "you basically have to\nconsult the documentation.",
        "start": 1551.01,
        "duration": 2.57
    },
    {
        "text": "The documentation for React\nNative is really good.",
        "start": 1553.58,
        "duration": 2.14
    },
    {
        "text": "I recommend that you\nperuse them just to see",
        "start": 1555.72,
        "duration": 2.03
    },
    {
        "text": "what components are available\nto you and those component APIs.",
        "start": 1557.75,
        "duration": 3.92
    },
    {
        "text": "And basically most of the\nstuff that you want to do",
        "start": 1561.67,
        "duration": 3.25
    },
    {
        "text": "is already pre-built for you.",
        "start": 1564.92,
        "duration": 1.742
    },
    {
        "text": "And so, even though\nthere's no such thing",
        "start": 1566.662,
        "duration": 1.708
    },
    {
        "text": "as a checkbox component in React Native,\nthere is actually a way to do that.",
        "start": 1568.37,
        "duration": 4.82
    },
    {
        "text": "And so let's go ahead\nand add this thing which",
        "start": 1573.19,
        "duration": 2.65
    },
    {
        "text": "is similar to a checkbox\nin that it's a Boolean flag",
        "start": 1575.84,
        "duration": 4.47
    },
    {
        "text": "but it's not really exactly\nstylistically the same.",
        "start": 1580.31,
        "duration": 3.462
    },
    {
        "text": "And so let's add this\nthing called a switch.",
        "start": 1583.772,
        "duration": 1.833
    },
    {
        "text": "As a switch you'll see what\nit looks like in a moment",
        "start": 1589.082,
        "duration": 3.428
    },
    {
        "text": "but it's basically just a Boolean flag\nthat we're going to use in this example",
        "start": 1592.51,
        "duration": 3.487
    },
    {
        "text": "rather than using a checkbox.",
        "start": 1595.997,
        "duration": 1.208
    },
    {
        "text": "So before what we had here was an\ninput of type checkbox and instead",
        "start": 1600.94,
        "duration": 4.04
    },
    {
        "text": "we're going to use a switch.",
        "start": 1604.98,
        "duration": 2.26
    },
    {
        "text": "And the value of that is going to be\nwhether the props.TODO is checked.",
        "start": 1607.24,
        "duration": 5.21
    },
    {
        "text": "And so now when we add\na TODO we see the switch",
        "start": 1616.7,
        "duration": 2.4
    },
    {
        "text": "that can be flipped back and forth.",
        "start": 1619.1,
        "duration": 2.41
    },
    {
        "text": "But if you notice, every\ntime I try to flip it on it",
        "start": 1621.51,
        "duration": 2.81
    },
    {
        "text": "immediately turns back off.",
        "start": 1624.32,
        "duration": 3.15
    },
    {
        "text": "Can anybody spot why that's happening?",
        "start": 1627.47,
        "duration": 2.7
    },
    {
        "text": "So we have this value set to props.TODO\nchecked, and down here do we ever",
        "start": 1634.97,
        "duration": 7.25
    },
    {
        "text": "update that value?",
        "start": 1642.22,
        "duration": 0.934
    },
    {
        "text": "No we don't.",
        "start": 1645.76,
        "duration": 0.81
    },
    {
        "text": "So we have this thing called Toggle\nTODO which we implemented last week,",
        "start": 1646.57,
        "duration": 3.93
    },
    {
        "text": "which, given some TODOs ID will\nflip that Boolean checked flag.",
        "start": 1650.5,
        "duration": 4.93
    },
    {
        "text": "But we never actually hook\nthat up for this example.",
        "start": 1655.43,
        "duration": 4.53
    },
    {
        "text": "So in the TODO component here\nwe're passing down an onToggle prop",
        "start": 1659.96,
        "duration": 4.97
    },
    {
        "text": "but we never actually use it up here.",
        "start": 1664.93,
        "duration": 2.52
    },
    {
        "text": "And so here we should actually\nhave the switch when we do on--",
        "start": 1667.45,
        "duration": 7.65
    },
    {
        "text": "what's it called-- on value change.",
        "start": 1675.1,
        "duration": 3.02
    },
    {
        "text": "And I only know this because\nthat's what the documentation says.",
        "start": 1678.12,
        "duration": 4.06
    },
    {
        "text": "And so when that value changed,\nI should run props.onToggle,",
        "start": 1682.18,
        "duration": 6.18
    },
    {
        "text": "which is the name of the\nprop that we're passing down",
        "start": 1688.36,
        "duration": 3.03
    },
    {
        "text": "from this parent component.",
        "start": 1691.39,
        "duration": 1.95
    },
    {
        "text": "And so now when we\nclick TODO it updates.",
        "start": 1693.34,
        "duration": 4.25
    },
    {
        "text": "And as you see right here the unchecked\nTODO count still updates as expected.",
        "start": 1697.59,
        "duration": 5.664
    },
    {
        "text": "And so now if we create a bunch\nwe can see those numbers changing.",
        "start": 1703.254,
        "duration": 3.986
    },
    {
        "text": "We can see the checking and\ntoggling works as expected.",
        "start": 1707.24,
        "duration": 2.75
    },
    {
        "text": "We see if we delete this\none the TODO count goes down",
        "start": 1709.99,
        "duration": 2.43
    },
    {
        "text": "but the uncheck count does not\ngo down since it was checked.",
        "start": 1712.42,
        "duration": 2.704
    },
    {
        "text": "If we delete something that isn't\nchecked, both of them go down.",
        "start": 1715.124,
        "duration": 2.666
    },
    {
        "text": "And so we have the same behavior as\nwe did in our React Web application.",
        "start": 1717.79,
        "duration": 5.917
    },
    {
        "text": "Any questions there?",
        "start": 1728.58,
        "duration": 1.18
    },
    {
        "text": "So we have this being a scroll view.",
        "start": 1735.2,
        "duration": 2.73
    },
    {
        "text": "But, if you notice, the\nscroll view gets cut off early",
        "start": 1737.93,
        "duration": 2.77
    },
    {
        "text": "and as we add TODOs it grows.",
        "start": 1740.7,
        "duration": 4.23
    },
    {
        "text": "But if we add a bunch of\nTODOs it grows with it.",
        "start": 1744.93,
        "duration": 11.59
    },
    {
        "text": "But say we actually wanted the scroll\nview to reach all the way to the bottom",
        "start": 1756.52,
        "duration": 6.54
    },
    {
        "text": "no matter how many TODOs were there.",
        "start": 1763.06,
        "duration": 2.25
    },
    {
        "text": "Does anybody know how we\nmay go about doing that?",
        "start": 1765.31,
        "duration": 3.37
    },
    {
        "text": "The hint being that in order\nto control layout what we use",
        "start": 1768.68,
        "duration": 2.687
    },
    {
        "text": "is this thing called Flexbox.",
        "start": 1771.367,
        "duration": 1.208
    },
    {
        "text": "So by default components\nwill grow to however big",
        "start": 1775.66,
        "duration": 4.83
    },
    {
        "text": "they need to be in order\nto fit their children.",
        "start": 1780.49,
        "duration": 3.48
    },
    {
        "text": "But we have a way of saying, hey fill\nas much space as you possibly can.",
        "start": 1783.97,
        "duration": 4.69
    },
    {
        "text": "And the way to do that\nis saying flex: 1.",
        "start": 1788.66,
        "duration": 3.65
    },
    {
        "text": "And so we want the app container\nto have a flex value of 1",
        "start": 1792.31,
        "duration": 3.94
    },
    {
        "text": "so that the app container\nfills up all possible space.",
        "start": 1796.25,
        "duration": 4.4
    },
    {
        "text": "And so we could do something like\napp container let's do flex: 1.",
        "start": 1800.65,
        "duration": 4.59
    },
    {
        "text": "And then maybe for the TODOs,\nthe scroll view here, maybe we",
        "start": 1805.24,
        "duration": 5.67
    },
    {
        "text": "want that to fill as well.",
        "start": 1810.91,
        "duration": 1.97
    },
    {
        "text": "And so we could go\ndown to the scroll view",
        "start": 1812.88,
        "duration": 2.74
    },
    {
        "text": "and say the style is\ngoing to be flex: 1.",
        "start": 1815.62,
        "duration": 5.61
    },
    {
        "text": "But that isn't great design.",
        "start": 1821.23,
        "duration": 2.61
    },
    {
        "text": "What if we wanted instead to just have\na style called Fill, which will just",
        "start": 1823.84,
        "duration": 5.43
    },
    {
        "text": "fill whatever space is available.",
        "start": 1829.27,
        "duration": 2.49
    },
    {
        "text": "And so that would be a\ngood abstraction to have.",
        "start": 1831.76,
        "duration": 2.772
    },
    {
        "text": "So here we have a TODO container,\nwe have an app container,",
        "start": 1834.532,
        "duration": 2.458
    },
    {
        "text": "and let's actually create this style\ncalled Fill, which we'll just flex: 1.",
        "start": 1836.99,
        "duration": 4.37
    },
    {
        "text": "And so now we can say hey, we\nwant this scroll view to fill",
        "start": 1845.8,
        "duration": 9.34
    },
    {
        "text": "and we also want our\napp container to fill.",
        "start": 1855.14,
        "duration": 5.37
    },
    {
        "text": "But instead of adding\nthat to app container,",
        "start": 1860.51,
        "duration": 3.23
    },
    {
        "text": "what would be a better way to do it?",
        "start": 1863.74,
        "duration": 1.78
    },
    {
        "text": "Well, we can actually\napply both those styles.",
        "start": 1865.52,
        "duration": 1.98
    },
    {
        "text": "Does anybody remember how we could\ndo that, apply multiple styles",
        "start": 1867.5,
        "duration": 3.09
    },
    {
        "text": "to the same component?",
        "start": 1870.59,
        "duration": 1.666
    },
    {
        "text": "So in React Web we would actually\njust give it multiple classes.",
        "start": 1875.68,
        "duration": 4.49
    },
    {
        "text": "What is the analog in React Native?",
        "start": 1880.17,
        "duration": 1.64
    },
    {
        "text": "We can actually just pass an array.",
        "start": 1884.88,
        "duration": 2.18
    },
    {
        "text": "And so say first apply\nstyles.Appcontainer and then apply",
        "start": 1887.06,
        "duration": 3.58
    },
    {
        "text": "styles.fill.",
        "start": 1890.64,
        "duration": 0.75
    },
    {
        "text": "And now, if we add a\nbunch of TODOs we can",
        "start": 1894.63,
        "duration": 4.23
    },
    {
        "text": "see that it fills the available space.",
        "start": 1898.86,
        "duration": 2.4
    },
    {
        "text": "And then if we delete TODOs such that\nit doesn't fill the available space",
        "start": 1901.26,
        "duration": 3.96
    },
    {
        "text": "we see that it's not getting\ncut off at the bottom",
        "start": 1905.22,
        "duration": 3.06
    },
    {
        "text": "because it's filling all the way\ndown to the bottom of this container.",
        "start": 1908.28,
        "duration": 5.64
    },
    {
        "text": "So any questions on event\nhandling, styling or moving",
        "start": 1913.92,
        "duration": 4.92
    },
    {
        "text": "React Web to React Native components?",
        "start": 1918.84,
        "duration": 2.355
    },
    {
        "text": "No.",
        "start": 1923.925,
        "duration": 1.301
    },
    {
        "text": "So we've been talking about\nthis thing called components,",
        "start": 1925.226,
        "duration": 2.374
    },
    {
        "text": "but we haven't really dived too\ndeeply into what that really means.",
        "start": 1927.6,
        "duration": 4.5
    },
    {
        "text": "In the past few weeks, we've\ntalked about how components",
        "start": 1932.1,
        "duration": 2.61
    },
    {
        "text": "return a node, how they\nrepresent a discrete piece of UI,",
        "start": 1934.71,
        "duration": 3.08
    },
    {
        "text": "how all components should act like pure\nfunctions with respect to their props.",
        "start": 1937.79,
        "duration": 4.01
    },
    {
        "text": "But that's really where we\nstopped talking about components.",
        "start": 1941.8,
        "duration": 2.69
    },
    {
        "text": "And so this week, we're going to\ndive more deeply into components",
        "start": 1944.49,
        "duration": 2.73
    },
    {
        "text": "and what components actually are.",
        "start": 1947.22,
        "duration": 2.797
    },
    {
        "text": "And so there are actually\ntwo types of components.",
        "start": 1950.017,
        "duration": 2.083
    },
    {
        "text": "And we've actually seen\nboth of them already.",
        "start": 1952.1,
        "duration": 2.05
    },
    {
        "text": "So first is this thing called a\nstateless functional component.",
        "start": 1954.15,
        "duration": 2.92
    },
    {
        "text": "You might see it abbreviated as SFC or\nif you're reading blog posts online,",
        "start": 1957.07,
        "duration": 3.38
    },
    {
        "text": "some people call them pure\nfunctional components.",
        "start": 1960.45,
        "duration": 2.95
    },
    {
        "text": "And what those are\nbasically just functions.",
        "start": 1963.4,
        "duration": 3.65
    },
    {
        "text": "So something like this\nTODO that we've created",
        "start": 1967.05,
        "duration": 3.06
    },
    {
        "text": "is just a function that takes\nin props and returns some node.",
        "start": 1970.11,
        "duration": 3.72
    },
    {
        "text": "It has no concept of state.",
        "start": 1973.83,
        "duration": 2.676
    },
    {
        "text": "And so that's why it's called a\nstateless functional component.",
        "start": 1976.506,
        "duration": 2.624
    },
    {
        "text": "It's just a function with no state.",
        "start": 1979.13,
        "duration": 2.41
    },
    {
        "text": "And the second is a\nreact.component which",
        "start": 1984.09,
        "duration": 1.86
    },
    {
        "text": "we've been extending from but we\nhaven't really talked about it",
        "start": 1985.95,
        "duration": 3.21
    },
    {
        "text": "too far in depth.",
        "start": 1989.16,
        "duration": 1.91
    },
    {
        "text": "And so first let's talk about\nstateless functional components.",
        "start": 1991.07,
        "duration": 3.041
    },
    {
        "text": "So this is the simplest\ntype of component.",
        "start": 1999.03,
        "duration": 2.21
    },
    {
        "text": "You should use this when\nyou don't need any state.",
        "start": 2001.24,
        "duration": 3.24
    },
    {
        "text": "And what it is is a function that\ntakes props and returns a node.",
        "start": 2004.48,
        "duration": 4.04
    },
    {
        "text": "And it shouldn't do anything other\nthan taking props and return a node.",
        "start": 2008.52,
        "duration": 3.34
    },
    {
        "text": "It should be what's\ncalled a pure function.",
        "start": 2011.86,
        "duration": 1.999
    },
    {
        "text": "In other words, it should not have\nany side effects, like setting a value",
        "start": 2013.859,
        "duration": 3.041
    },
    {
        "text": "or pushing to an array, updating\nan object, something like that",
        "start": 2016.9,
        "duration": 4.86
    },
    {
        "text": "because it should just take\nin props and return the value.",
        "start": 2021.76,
        "duration": 4.2
    },
    {
        "text": "If you do stuff other than that you\nmight create some bugs or even worse",
        "start": 2025.96,
        "duration": 5.4
    },
    {
        "text": "crash your app or something like that.",
        "start": 2031.36,
        "duration": 3.264
    },
    {
        "text": "Then, any changes to the\nprops that you passed",
        "start": 2034.624,
        "duration": 1.916
    },
    {
        "text": "to a stateless functional\ncomponent will automatically",
        "start": 2036.54,
        "duration": 2.68
    },
    {
        "text": "cause that function to be re-invoked.",
        "start": 2039.22,
        "duration": 2.65
    },
    {
        "text": "And then after it re-invokes\nthe function and returns nodes,",
        "start": 2041.87,
        "duration": 3.2
    },
    {
        "text": "React will do its thing and compare\nnodes to what it has in its virtual dom",
        "start": 2045.07,
        "duration": 4.407
    },
    {
        "text": "and then go ahead and\nreplace what's needed.",
        "start": 2049.477,
        "duration": 1.833
    },
    {
        "text": "And so on the other side of the coin,\nwe have what's called a React.component.",
        "start": 2054.06,
        "duration": 3.966
    },
    {
        "text": "This is something that's actually\nprovided by the React library",
        "start": 2058.026,
        "duration": 2.624
    },
    {
        "text": "and implemented for you.",
        "start": 2060.65,
        "duration": 1.68
    },
    {
        "text": "And it's an abstract class that can be\nextended to behave however you want.",
        "start": 2062.33,
        "duration": 3.82
    },
    {
        "text": "And so, in our example\nhere and examples prior,",
        "start": 2066.15,
        "duration": 3.299
    },
    {
        "text": "we've been doing this thing where we\ncreate a class called whatever we want",
        "start": 2069.449,
        "duration": 3.421
    },
    {
        "text": "and we're actually extending this\nthing called a React component.",
        "start": 2072.87,
        "duration": 4.53
    },
    {
        "text": "And so what is a React.component?",
        "start": 2077.4,
        "duration": 3.981
    },
    {
        "text": "Well these things have\nadditional features",
        "start": 2081.381,
        "duration": 1.749
    },
    {
        "text": "that stateless functional\ncomponents do not.",
        "start": 2083.13,
        "duration": 2.46
    },
    {
        "text": "One of those, of course, is that they\nhave instances so they're a class.",
        "start": 2085.59,
        "duration": 3.247
    },
    {
        "text": "And so when you invoke that\nclass it returns an instance",
        "start": 2088.837,
        "duration": 2.333
    },
    {
        "text": "and that instance will persist\nthroughout the lifetime of this class.",
        "start": 2091.17,
        "duration": 5.719
    },
    {
        "text": "As suggested by the name,\nit maintains its own state",
        "start": 2096.889,
        "duration": 3.341
    },
    {
        "text": "and so stateless components do not,\nwhereas these React components do.",
        "start": 2100.23,
        "duration": 4.62
    },
    {
        "text": "They have this concept of\nstate, and we talked about state",
        "start": 2104.85,
        "duration": 2.58
    },
    {
        "text": "in depth last lecture.",
        "start": 2107.43,
        "duration": 0.96
    },
    {
        "text": "One thing we didn't\ntalk about last lecture",
        "start": 2111.399,
        "duration": 1.791
    },
    {
        "text": "is this thing called a lifecycle,\nit's lifecycle methods.",
        "start": 2113.19,
        "duration": 3.395
    },
    {
        "text": "And so these are similar\nto hooks or event handlers.",
        "start": 2116.585,
        "duration": 2.595
    },
    {
        "text": "And so we've used the event handlers\nbefore in both React Web and React",
        "start": 2119.18,
        "duration": 4.17
    },
    {
        "text": "Native.",
        "start": 2123.35,
        "duration": 1.29
    },
    {
        "text": "And these things are actually\nautomatically invoked for you.",
        "start": 2124.64,
        "duration": 2.56
    },
    {
        "text": "You don't have to worry about\nexactly the implementation details",
        "start": 2127.2,
        "duration": 3.65
    },
    {
        "text": "or when to invoke your own functions.",
        "start": 2130.85,
        "duration": 1.9
    },
    {
        "text": "That's actually something\nthat's done automatically.",
        "start": 2132.75,
        "duration": 4.13
    },
    {
        "text": "And so unlike stateless\nfunctional components,",
        "start": 2136.88,
        "duration": 2.43
    },
    {
        "text": "which just take props and return a\nnode, a React components render function",
        "start": 2139.31,
        "duration": 4.68
    },
    {
        "text": "actually becomes a function of\nthe props and also any class",
        "start": 2143.99,
        "duration": 3.06
    },
    {
        "text": "properties that exist.",
        "start": 2147.05,
        "duration": 1.06
    },
    {
        "text": "And so if you remember back to last\nlecture we talked about classes",
        "start": 2148.11,
        "duration": 3.44
    },
    {
        "text": "and how when you create\na class instance,",
        "start": 2151.55,
        "duration": 1.96
    },
    {
        "text": "you might attach to it some properties.",
        "start": 2153.51,
        "duration": 2.1
    },
    {
        "text": "These properties can be\nvalues anywhere from functions",
        "start": 2155.61,
        "duration": 3.23
    },
    {
        "text": "to just primitives, objects.",
        "start": 2158.84,
        "duration": 3.78
    },
    {
        "text": "And so when you create a\nclass component instance,",
        "start": 2162.62,
        "duration": 3.19
    },
    {
        "text": "you can actually use all of those\nclass properties in that render method.",
        "start": 2165.81,
        "duration": 5.85
    },
    {
        "text": "And so we saw that over here\nwhen we created this addTODO",
        "start": 2171.66,
        "duration": 7.04
    },
    {
        "text": "where within the render we referenced\nthis.addTODO in this button component",
        "start": 2178.7,
        "duration": 6.99
    },
    {
        "text": "here.",
        "start": 2185.69,
        "duration": 1.401
    },
    {
        "text": "And so, as you see, this is a\nclass property which we actually",
        "start": 2187.091,
        "duration": 3.249
    },
    {
        "text": "used in our render method.",
        "start": 2190.34,
        "duration": 1.56
    },
    {
        "text": "And so this render method is\nactually a function of both props",
        "start": 2191.9,
        "duration": 4.29
    },
    {
        "text": "and any class properties like its\nstate or these methods that we defined.",
        "start": 2196.19,
        "duration": 5.33
    },
    {
        "text": "Cool.",
        "start": 2204.72,
        "duration": 0.5
    },
    {
        "text": "So I talked about this thing\ncalled a lifecycle method,",
        "start": 2205.22,
        "duration": 2.74
    },
    {
        "text": "but what actually is\na component lifecycle.",
        "start": 2207.96,
        "duration": 3.08
    },
    {
        "text": "And so a component lifecycle can\nactually be represented by this graph.",
        "start": 2211.04,
        "duration": 3.89
    },
    {
        "text": "And so first a component will\nmount and so some lifecycle hooks",
        "start": 2214.93,
        "duration": 4.48
    },
    {
        "text": "get called there, but that's\nbasically that constructor where",
        "start": 2219.41,
        "duration": 4.06
    },
    {
        "text": "the class instance gets created and\nmaybe its state gets instantiated.",
        "start": 2223.47,
        "duration": 5.48
    },
    {
        "text": "And then what it does is it renders.",
        "start": 2228.95,
        "duration": 2.4
    },
    {
        "text": "It will just put you to the page.",
        "start": 2231.35,
        "duration": 3.03
    },
    {
        "text": "And then every time we call set\nstate or get new props we actually",
        "start": 2234.38,
        "duration": 3.21
    },
    {
        "text": "enter what's called an update cycle.",
        "start": 2237.59,
        "duration": 1.78
    },
    {
        "text": "And so when you receive new props,\nthe component needs to update.",
        "start": 2239.37,
        "duration": 2.97
    },
    {
        "text": "It needs to re-render.",
        "start": 2242.34,
        "duration": 1.44
    },
    {
        "text": "And so part of its lifecycle is\nactually updating over and over.",
        "start": 2243.78,
        "duration": 3.69
    },
    {
        "text": "And this happens any time new props\nget received because it wouldn't really",
        "start": 2247.47,
        "duration": 3.53
    },
    {
        "text": "make sense if we had\na component that when",
        "start": 2251.0,
        "duration": 2.13
    },
    {
        "text": "it received new props nothing changed.",
        "start": 2253.13,
        "duration": 2.61
    },
    {
        "text": "But also this update cycle happens\nevery single time the state changes.",
        "start": 2255.74,
        "duration": 3.88
    },
    {
        "text": "So if you call this .setstate, you\nupdate state and presumably you have",
        "start": 2259.62,
        "duration": 4.19
    },
    {
        "text": "something in the UI that also updates.",
        "start": 2263.81,
        "duration": 1.74
    },
    {
        "text": "And so this update\ncycle will happen again.",
        "start": 2265.55,
        "duration": 2.04
    },
    {
        "text": "And every single time you update state,\nreceive new props this update cycle",
        "start": 2267.59,
        "duration": 3.43
    },
    {
        "text": "will fire again.",
        "start": 2271.02,
        "duration": 1.67
    },
    {
        "text": "And then, when it's time for\nthat component to disappear,",
        "start": 2272.69,
        "duration": 2.96
    },
    {
        "text": "it enters what's called\nthe unmount stage where",
        "start": 2275.65,
        "duration": 3.91
    },
    {
        "text": "you have the chance to\nclean up anything that you",
        "start": 2279.56,
        "duration": 3.0
    },
    {
        "text": "may have created during that lifecycle.",
        "start": 2282.56,
        "duration": 4.44
    },
    {
        "text": "And so what actually does\nthat mean in practice?",
        "start": 2287.0,
        "duration": 3.652
    },
    {
        "text": "So I said that there's\nthis thing called mount,",
        "start": 2290.652,
        "duration": 1.958
    },
    {
        "text": "which is basically\njust a series of steps",
        "start": 2292.61,
        "duration": 2.04
    },
    {
        "text": "that happens when a component\nfirst gets mounted and rendered.",
        "start": 2294.65,
        "duration": 3.189
    },
    {
        "text": "And so the first thing that happens\nis the constructor gets called.",
        "start": 2297.839,
        "duration": 2.791
    },
    {
        "text": "And so, as we saw a few lectures\nago when we talked about classes,",
        "start": 2300.63,
        "duration": 3.35
    },
    {
        "text": "the constructor is where we have\na chance to add class properties",
        "start": 2303.98,
        "duration": 4.11
    },
    {
        "text": "or add anything to that\ninstance that we need.",
        "start": 2308.09,
        "duration": 3.3
    },
    {
        "text": "And so here we might want to\ndo stuff like initialize state",
        "start": 2311.39,
        "duration": 2.52
    },
    {
        "text": "or maybe add some other class\nproperties like bound methods et cetera.",
        "start": 2313.91,
        "duration": 5.52
    },
    {
        "text": "Next what happens is we render, which\nis just the meat of the component.",
        "start": 2319.43,
        "duration": 5.33
    },
    {
        "text": "The main goal of any\ncomponent is to show you why.",
        "start": 2324.76,
        "duration": 4.24
    },
    {
        "text": "And so, in this render method,\nthat's exactly what happens.",
        "start": 2329.0,
        "duration": 4.08
    },
    {
        "text": "You take any properties that you have,\nany class properties that you have,",
        "start": 2333.08,
        "duration": 4.66
    },
    {
        "text": "and then you end up returning a node.",
        "start": 2337.74,
        "duration": 3.209
    },
    {
        "text": "And then after that this hook,\nthat we haven't seen yet, gets",
        "start": 2340.949,
        "duration": 2.541
    },
    {
        "text": "called a component div mount.",
        "start": 2343.49,
        "duration": 1.646
    },
    {
        "text": "And this is the chance\nfor you to do anything",
        "start": 2345.136,
        "duration": 1.874
    },
    {
        "text": "that you wanted to do that\ndidn't really matter for render.",
        "start": 2347.01,
        "duration": 4.285
    },
    {
        "text": "And so if you have asynched actions,\nlike standing network or passes.",
        "start": 2351.295,
        "duration": 2.875
    },
    {
        "text": "If you want to add timers\nand stuff like that this",
        "start": 2354.17,
        "duration": 3.57
    },
    {
        "text": "is exactly where you should do that.",
        "start": 2357.74,
        "duration": 3.31
    },
    {
        "text": "And then maybe you'll need to\nupdate the state accordingly.",
        "start": 2361.05,
        "duration": 3.32
    },
    {
        "text": "And so if you actually\nsee that state here",
        "start": 2364.37,
        "duration": 2.01
    },
    {
        "text": "this will cause a re-render\nwithout updating the UI.",
        "start": 2366.38,
        "duration": 2.36
    },
    {
        "text": "And so all of this will happen\nbefore the UI re-renders.",
        "start": 2368.74,
        "duration": 3.57
    },
    {
        "text": "And so let's play with\nthat a little bit.",
        "start": 2372.31,
        "duration": 2.89
    },
    {
        "text": "So first let's copy this,\nthat way you can keep it.",
        "start": 2375.2,
        "duration": 3.81
    },
    {
        "text": "So let's clear all of this and then\nplay with mounting a little bit.",
        "start": 2389.01,
        "duration": 8.76
    },
    {
        "text": "And so in your next project what\nyou're going to do is you're",
        "start": 2397.77,
        "duration": 3.27
    },
    {
        "text": "going to be implementing\nwhat's called a Pomodoro timer.",
        "start": 2401.04,
        "duration": 3.76
    },
    {
        "text": "And so for those of you who\nare aware of what those are--",
        "start": 2404.8,
        "duration": 3.47
    },
    {
        "text": "basically what it is is\na timer that allows you",
        "start": 2408.27,
        "duration": 3.06
    },
    {
        "text": "to switch between two amounts of time.",
        "start": 2411.33,
        "duration": 3.069
    },
    {
        "text": "And so there's this thing called\nthe Pomodoro Technique which",
        "start": 2414.399,
        "duration": 2.541
    },
    {
        "text": "is used for studying where you study or\nwork very hard for some amount of time",
        "start": 2416.94,
        "duration": 4.187
    },
    {
        "text": "and then you take a short break.",
        "start": 2421.127,
        "duration": 1.333
    },
    {
        "text": "And then you work hard for\nsome short amount of time",
        "start": 2422.46,
        "duration": 2.166
    },
    {
        "text": "and then you take a short break.",
        "start": 2424.626,
        "duration": 1.605
    },
    {
        "text": "And so what you're going to be\ncreating in your next project",
        "start": 2426.231,
        "duration": 2.499
    },
    {
        "text": "is actually a timer that\nallows you to do that.",
        "start": 2428.73,
        "duration": 2.46
    },
    {
        "text": "It will automatically track for\nyou however long you want to work.",
        "start": 2431.19,
        "duration": 4.79
    },
    {
        "text": "And it will also allow\nyou to set some time",
        "start": 2435.98,
        "duration": 2.227
    },
    {
        "text": "that you want to take a break\nin between those working blocks.",
        "start": 2438.207,
        "duration": 2.583
    },
    {
        "text": "And it will do that.",
        "start": 2440.79,
        "duration": 0.833
    },
    {
        "text": "So when you start the timer it will\ncount down until you're done working.",
        "start": 2441.623,
        "duration": 3.787
    },
    {
        "text": "It will let you know,\nhey time for a break.",
        "start": 2445.41,
        "duration": 2.28
    },
    {
        "text": "Then it will switch over\nto that break timer,",
        "start": 2447.69,
        "duration": 1.98
    },
    {
        "text": "run down until that ends up and\nsays, oh now it's time to work,",
        "start": 2449.67,
        "duration": 3.12
    },
    {
        "text": "and it will cycle through that.",
        "start": 2452.79,
        "duration": 1.82
    },
    {
        "text": "And so in order to do\nthat, you might need",
        "start": 2454.61,
        "duration": 1.75
    },
    {
        "text": "to know how to work things like timers.",
        "start": 2456.36,
        "duration": 2.85
    },
    {
        "text": "And so these methods may be a chance\nfor you to set up those timers.",
        "start": 2459.21,
        "duration": 5.41
    },
    {
        "text": "And so let's go ahead and\ndo an example doing that.",
        "start": 2464.62,
        "duration": 3.08
    },
    {
        "text": "So first let's get rid\nof all of this stuff.",
        "start": 2467.7,
        "duration": 6.22
    },
    {
        "text": "So in this example we\nno longer need TODOs.",
        "start": 2473.92,
        "duration": 4.27
    },
    {
        "text": "And in our render lets\nactually just have some count.",
        "start": 2478.19,
        "duration": 4.88
    },
    {
        "text": "Those have a View.",
        "start": 2483.07,
        "duration": 0.75
    },
    {
        "text": "And inside here let's have some text.",
        "start": 2488.62,
        "duration": 1.96
    },
    {
        "text": "And that text is just\ngoing to show some count.",
        "start": 2496.27,
        "duration": 2.1
    },
    {
        "text": "And let's initialize that count to 0.",
        "start": 2505.04,
        "duration": 1.67
    },
    {
        "text": "So, as soon as I get rid of all this, we\nhave a very simple app and all it does",
        "start": 2515.55,
        "duration": 5.31
    },
    {
        "text": "is show a count of 0.",
        "start": 2520.86,
        "duration": 1.07
    },
    {
        "text": "You see it up in this\nleft hand corner here.",
        "start": 2521.93,
        "duration": 2.49
    },
    {
        "text": "And let's go ahead and\nactually center this.",
        "start": 2524.42,
        "duration": 1.88
    },
    {
        "text": "So let's do styles, and let's\ncreate a new style sheet.",
        "start": 2526.3,
        "duration": 6.74
    },
    {
        "text": "Let's call this app container and\nwhatever we want to do in here.",
        "start": 2537.42,
        "duration": 3.91
    },
    {
        "text": "So let's have it grow as much as we can.",
        "start": 2541.33,
        "duration": 2.719
    },
    {
        "text": "Let's have it center its items.",
        "start": 2544.049,
        "duration": 1.291
    },
    {
        "text": "And let's have it align its items\nthe other direction as well.",
        "start": 2549.69,
        "duration": 4.95
    },
    {
        "text": "And down here let's actually pass\nthis in as styles.appcontainer.",
        "start": 2562.24,
        "duration": 4.76
    },
    {
        "text": "So now we see this\nnumber 0 is very small.",
        "start": 2573.0,
        "duration": 1.97
    },
    {
        "text": "Let's go ahead and make\nit a little bit bigger.",
        "start": 2574.97,
        "duration": 2.73
    },
    {
        "text": "And so let's have count and\nlet's give it a big font",
        "start": 2577.7,
        "duration": 4.65
    },
    {
        "text": "size of like 48 or something.",
        "start": 2582.35,
        "duration": 3.669
    },
    {
        "text": "So now-- style--",
        "start": 2592.87,
        "duration": 4.94
    },
    {
        "text": "we have a big number\nand all it does is 0.",
        "start": 2597.81,
        "duration": 2.16
    },
    {
        "text": "And so how are we going\nto get it to count?",
        "start": 2599.97,
        "duration": 2.43
    },
    {
        "text": "Well presumably we should\nbe setting our state",
        "start": 2602.4,
        "duration": 2.25
    },
    {
        "text": "and just have that state increase.",
        "start": 2604.65,
        "duration": 4.05
    },
    {
        "text": "And so if we want to repeat something\nwhat might we use to achieve that?",
        "start": 2608.7,
        "duration": 5.69
    },
    {
        "text": "So do something at some given interval.",
        "start": 2618.21,
        "duration": 3.81
    },
    {
        "text": "We can actually use that set interval.",
        "start": 2622.02,
        "duration": 2.83
    },
    {
        "text": "And so let's first implement this count.",
        "start": 2624.85,
        "duration": 2.2
    },
    {
        "text": "So let's have this\nthing called increment.",
        "start": 2627.05,
        "duration": 2.1
    },
    {
        "text": "Is this too small?",
        "start": 2629.15,
        "duration": 3.44
    },
    {
        "text": "Let's have this thing called ink.",
        "start": 2632.59,
        "duration": 2.05
    },
    {
        "text": "And what that does is it does\nthis.setstate, takes a previous state",
        "start": 2634.64,
        "duration": 8.81
    },
    {
        "text": "and returns the count to be 1\ngreater than the previous state.",
        "start": 2643.45,
        "duration": 4.74
    },
    {
        "text": "And so now we've implemented this\nthing called increment where we",
        "start": 2653.45,
        "duration": 4.77
    },
    {
        "text": "take the states count and increment it.",
        "start": 2658.22,
        "duration": 3.25
    },
    {
        "text": "And so how might we get this increment\ncall to happen every once in a while?",
        "start": 2661.47,
        "duration": 6.497
    },
    {
        "text": "Well presumably we\nshould use a thing called",
        "start": 2667.967,
        "duration": 1.833
    },
    {
        "text": "set interval, which we'll call\na function every n milliseconds.",
        "start": 2669.8,
        "duration": 4.35
    },
    {
        "text": "But how are we going\nto get that to happen?",
        "start": 2674.15,
        "duration": 3.219
    },
    {
        "text": "Well we should do this after\nthe component finishes mounting.",
        "start": 2677.369,
        "duration": 2.541
    },
    {
        "text": "We should set up some sort of timer.",
        "start": 2679.91,
        "duration": 2.33
    },
    {
        "text": "And so how do we know or\nhow do we get a function",
        "start": 2682.24,
        "duration": 2.26
    },
    {
        "text": "to execute after\ncomponents finish mounting?",
        "start": 2684.5,
        "duration": 4.73
    },
    {
        "text": "That's actually where this\nlifecycle method comes in.",
        "start": 2689.23,
        "duration": 2.519
    },
    {
        "text": "And so there's this\nlifecycle method called",
        "start": 2691.749,
        "duration": 1.791
    },
    {
        "text": "componentDidMount which\nautomatically gets",
        "start": 2693.54,
        "duration": 2.54
    },
    {
        "text": "run for after the component mounts.",
        "start": 2696.08,
        "duration": 2.63
    },
    {
        "text": "And so we can actually set\nup our timer tap in there.",
        "start": 2698.71,
        "duration": 3.38
    },
    {
        "text": "And so we can do componentDidMount\nand inside of it we can do setInterval",
        "start": 2702.09,
        "duration": 8.42
    },
    {
        "text": "and that's called\nthis.Increment every second.",
        "start": 2710.51,
        "duration": 5.58
    },
    {
        "text": "And so there's going\nto be a small bug here.",
        "start": 2716.09,
        "duration": 4.56
    },
    {
        "text": "Does anybody know what the bug is?",
        "start": 2720.65,
        "duration": 3.25
    },
    {
        "text": "So every 1,000 milliseconds this\nthing called this.Increment is getting",
        "start": 2727.08,
        "duration": 3.81
    },
    {
        "text": "called.",
        "start": 2730.89,
        "duration": 1.0
    },
    {
        "text": "And this.Increment is\ninvoking this.Setstate.",
        "start": 2731.89,
        "duration": 3.42
    },
    {
        "text": "Does anybody see how\nthat might be a problem?",
        "start": 2737.98,
        "duration": 3.206
    },
    {
        "text": "I'll give you a hint.",
        "start": 2747.15,
        "duration": 0.99
    },
    {
        "text": "It has something to do with this.",
        "start": 2748.14,
        "duration": 4.52
    },
    {
        "text": "And so when this gets executed this\nmight not mean what this is here.",
        "start": 2752.66,
        "duration": 4.83
    },
    {
        "text": "And so this is a common bug in React.",
        "start": 2757.49,
        "duration": 1.94
    },
    {
        "text": "Oftentimes, when you say\nthis here, what it means",
        "start": 2759.43,
        "duration": 4.59
    },
    {
        "text": "lexically is not\nnecessarily what it means",
        "start": 2764.02,
        "duration": 2.13
    },
    {
        "text": "when it actually eventually gets run.",
        "start": 2766.15,
        "duration": 2.16
    },
    {
        "text": "And so how did we go about fixing\nthis bug in previous lectures?",
        "start": 2768.31,
        "duration": 7.06
    },
    {
        "text": "We have to somehow get this to be\nbound to what we want it to be.",
        "start": 2775.37,
        "duration": 3.81
    },
    {
        "text": "And in case we want it\nto be bound lexically.",
        "start": 2779.18,
        "duration": 4.27
    },
    {
        "text": "So a few different ways to do that.",
        "start": 2783.45,
        "duration": 1.93
    },
    {
        "text": "One way was creating a new function\nhere in line that does this.",
        "start": 2785.38,
        "duration": 4.22
    },
    {
        "text": "And I'm actually not sure that\nthat works in this example",
        "start": 2793.0,
        "duration": 5.39
    },
    {
        "text": "because this isn't necessarily set here.",
        "start": 2798.39,
        "duration": 3.18
    },
    {
        "text": "The way we've generally handled\nthis is by actually binding it",
        "start": 2801.57,
        "duration": 7.12
    },
    {
        "text": "at creation time.",
        "start": 2808.69,
        "duration": 2.54
    },
    {
        "text": "And so there's a\nshorthand whereby we can",
        "start": 2811.23,
        "duration": 10.79
    },
    {
        "text": "say when we create this\nincrement function automatically",
        "start": 2822.02,
        "duration": 4.5
    },
    {
        "text": "bind it to this class.",
        "start": 2826.52,
        "duration": 2.01
    },
    {
        "text": "And so this is actually a new\naddition to the ECMAScript standard",
        "start": 2828.53,
        "duration": 6.33
    },
    {
        "text": "where this is called\nclass properties whereby",
        "start": 2834.86,
        "duration": 2.34
    },
    {
        "text": "inline as we're declaring\nthis class we can also",
        "start": 2837.2,
        "duration": 2.97
    },
    {
        "text": "create properties that should\nbe added during the constructor.",
        "start": 2840.17,
        "duration": 3.7
    },
    {
        "text": "And so this is syntactically\nthe same as doing this.",
        "start": 2843.87,
        "duration": 6.41
    },
    {
        "text": "Having the increment function\ndefined as we did before.",
        "start": 2850.28,
        "duration": 9.79
    },
    {
        "text": "And in the constructor\nwhen this is created",
        "start": 2860.07,
        "duration": 2.02
    },
    {
        "text": "doing this.Increment equals\nthis.Increment.bind whatever",
        "start": 2862.09,
        "duration": 9.4
    },
    {
        "text": "the this context we want to be.",
        "start": 2871.49,
        "duration": 2.29
    },
    {
        "text": "And in this case it's this.",
        "start": 2873.78,
        "duration": 3.06
    },
    {
        "text": "Or in other words, it's\nthe same as just doing",
        "start": 2876.84,
        "duration": 2.16
    },
    {
        "text": "this.Increment is equal to the anonymous\nfunction that we defined down there.",
        "start": 2879.0,
        "duration": 4.01
    },
    {
        "text": "Whatever.",
        "start": 2887.03,
        "duration": 2.58
    },
    {
        "text": "And so that's just, rather than having\nto write everything in the constructor,",
        "start": 2889.61,
        "duration": 5.56
    },
    {
        "text": "we can just use this\nshorthand down here which",
        "start": 2895.17,
        "duration": 7.68
    },
    {
        "text": "is just generally the preferred\nway because it's easier to read.",
        "start": 2902.85,
        "duration": 6.164
    },
    {
        "text": "And now we've gone ahead and\ncreated this timer that runs.",
        "start": 2909.014,
        "duration": 2.416
    },
    {
        "text": "And so you can see that\nthe numbers are going up.",
        "start": 2911.43,
        "duration": 3.277
    },
    {
        "text": "And the reason that this is happening\nis because we created this increment",
        "start": 2914.707,
        "duration": 3.083
    },
    {
        "text": "function.",
        "start": 2917.79,
        "duration": 0.75
    },
    {
        "text": "We correctly bound it to the\nthis that we wanted to bind it to",
        "start": 2918.54,
        "duration": 3.177
    },
    {
        "text": "and then we said, hey,\ncomponent when you're",
        "start": 2921.717,
        "duration": 1.833
    },
    {
        "text": "done mounting set up this timer, set up\non an interval of 1,000 milliseconds.",
        "start": 2923.55,
        "duration": 5.32
    },
    {
        "text": "So every second call\nthis increment function.",
        "start": 2928.87,
        "duration": 2.522
    },
    {
        "text": "And what does that\nincrement function do?",
        "start": 2931.392,
        "duration": 1.708
    },
    {
        "text": "Well it updates the state to be\nthe previous states count plus 1",
        "start": 2933.1,
        "duration": 3.5
    },
    {
        "text": "and then down in the render\nwe render this.state.count.",
        "start": 2936.6,
        "duration": 3.3
    },
    {
        "text": "And so you see every second the\nstate gets updated to a new number,",
        "start": 2939.9,
        "duration": 4.17
    },
    {
        "text": "and the new number is shown there.",
        "start": 2944.07,
        "duration": 2.46
    },
    {
        "text": "And so we never had to manually say\nhey, run this code when you mount.",
        "start": 2946.53,
        "duration": 9.15
    },
    {
        "text": "We just created this method called\ncomponent.DidMount and React handles",
        "start": 2955.68,
        "duration": 5.28
    },
    {
        "text": "automatically invoking that for\nyou after the component mounted.",
        "start": 2960.96,
        "duration": 2.82
    },
    {
        "text": "And it's the same as the constructor.",
        "start": 2967.59,
        "duration": 2.08
    },
    {
        "text": "We never had to manually\ninvoke the constructor.",
        "start": 2969.67,
        "duration": 2.08
    },
    {
        "text": "It just gets called automatically when\na class instance is getting created?",
        "start": 2971.75,
        "duration": 3.65
    },
    {
        "text": "Any questions on the mount cycle or\nthe mount processor I should say?",
        "start": 2978.22,
        "duration": 5.25
    },
    {
        "text": "Great so now let's talk\nabout the update cycle.",
        "start": 2991.01,
        "duration": 4.23
    },
    {
        "text": "And so, just like in\nthe mounting process,",
        "start": 2995.24,
        "duration": 2.17
    },
    {
        "text": "there is a bunch of lifecycle hooks\nthat got called for you automatically.",
        "start": 2997.41,
        "duration": 3.35
    },
    {
        "text": "There are also a bunch\nof lifecycle hooks",
        "start": 3000.76,
        "duration": 1.708
    },
    {
        "text": "that get called automatically every\nsingle time we want to re-render.",
        "start": 3002.468,
        "duration": 4.762
    },
    {
        "text": "And so the first thing\nthat happens is component",
        "start": 3007.23,
        "duration": 2.38
    },
    {
        "text": "will receive props which\ntakes the next props.",
        "start": 3009.61,
        "duration": 3.54
    },
    {
        "text": "And so say you had\nsomething in your state",
        "start": 3013.15,
        "duration": 2.1
    },
    {
        "text": "that really depended on\nwhat the props were set to,",
        "start": 3015.25,
        "duration": 3.744
    },
    {
        "text": "you can actually use this function\nto update any of those state fields",
        "start": 3018.994,
        "duration": 2.916
    },
    {
        "text": "that rely on the props.",
        "start": 3021.91,
        "duration": 1.51
    },
    {
        "text": "And you do that by\ncalling this .setstate.",
        "start": 3023.42,
        "duration": 2.9
    },
    {
        "text": "Next is this thing called\nshouldComponentUpdate,",
        "start": 3026.32,
        "duration": 3.15
    },
    {
        "text": "which takes the next\nprops and the next date,",
        "start": 3029.47,
        "duration": 2.94
    },
    {
        "text": "and here you can compare change\nvalues and decide whether or not",
        "start": 3032.41,
        "duration": 3.54
    },
    {
        "text": "you want that component to render.",
        "start": 3035.95,
        "duration": 1.47
    },
    {
        "text": "And you can actually stop\nthe update cycle here.",
        "start": 3037.42,
        "duration": 4.14
    },
    {
        "text": "And so this is a good optimization.",
        "start": 3044.26,
        "duration": 2.1
    },
    {
        "text": "So say you have a very\ncomplicated component",
        "start": 3046.36,
        "duration": 2.14
    },
    {
        "text": "that takes a really long time\nto render you don't necessarily",
        "start": 3048.5,
        "duration": 3.54
    },
    {
        "text": "want it to render every\nsingle time you get a new prop",
        "start": 3052.04,
        "duration": 3.18
    },
    {
        "text": "because it might be that the\nnew prop doesn't actually",
        "start": 3055.22,
        "duration": 2.25
    },
    {
        "text": "change anything that's shown.",
        "start": 3057.47,
        "duration": 2.04
    },
    {
        "text": "And so you could use this\nmethod to stop it early.",
        "start": 3059.51,
        "duration": 4.02
    },
    {
        "text": "But that adds a lot of\ncomplexity to your app",
        "start": 3063.53,
        "duration": 1.89
    },
    {
        "text": "and there's almost always\na premature optimization.",
        "start": 3065.42,
        "duration": 3.45
    },
    {
        "text": "The next happens render, we\nknow exactly what happens there.",
        "start": 3068.87,
        "duration": 4.02
    },
    {
        "text": "And last we have this thing\ncalled ComponentDidUpdate,",
        "start": 3072.89,
        "duration": 3.06
    },
    {
        "text": "whereby you can do anything\nthat isn't needed for the UI,",
        "start": 3075.95,
        "duration": 3.06
    },
    {
        "text": "like network requests,\nwhich is basically",
        "start": 3079.01,
        "duration": 2.25
    },
    {
        "text": "the analog for ComponentDidMount.",
        "start": 3081.26,
        "duration": 2.69
    },
    {
        "text": "And so let's see an\nexample for this update.",
        "start": 3083.95,
        "duration": 3.17
    },
    {
        "text": "So say rather than just\nrendering this text we actually",
        "start": 3087.12,
        "duration": 8.78
    },
    {
        "text": "pass this count to another function.",
        "start": 3095.9,
        "duration": 3.16
    },
    {
        "text": "So let's have this thing called a\ncount, which takes as a propped account.",
        "start": 3099.06,
        "duration": 10.29
    },
    {
        "text": "And then let's create\nthis class called count.",
        "start": 3114.47,
        "duration": 3.05
    },
    {
        "text": "And then here, let's first\njust render the text.",
        "start": 3122.61,
        "duration": 3.315
    },
    {
        "text": "And so now we're back to where\nwe started, where we basically",
        "start": 3132.16,
        "duration": 10.8
    },
    {
        "text": "have some text that gets rendered\nbased on this.PropsAccount,",
        "start": 3142.96,
        "duration": 4.73
    },
    {
        "text": "and let's style it to be larger.",
        "start": 3147.69,
        "duration": 2.87
    },
    {
        "text": "And so now we're basically back\nto exactly where we started.",
        "start": 3158.201,
        "duration": 2.499
    },
    {
        "text": "We have this app which\nautomatically increments",
        "start": 3160.7,
        "duration": 4.7
    },
    {
        "text": "and then it passes whatever its\nstate count is as the count prop",
        "start": 3165.4,
        "duration": 3.51
    },
    {
        "text": "to this other class that we call count.",
        "start": 3168.91,
        "duration": 4.22
    },
    {
        "text": "And then this component\nwe basically just take",
        "start": 3173.13,
        "duration": 2.35
    },
    {
        "text": "that prop and render that text.",
        "start": 3175.48,
        "duration": 4.11
    },
    {
        "text": "But say we actually only wanted\nto update on odd numbers.",
        "start": 3179.59,
        "duration": 5.94
    },
    {
        "text": "So say we want to create a new--",
        "start": 3185.53,
        "duration": 4.1
    },
    {
        "text": "or say we want to have this\nbe called CountEvennumbers.",
        "start": 3189.63,
        "duration": 5.39
    },
    {
        "text": "And so, in this example\nhere, how might we say,",
        "start": 3203.29,
        "duration": 4.79
    },
    {
        "text": "hey don't actually update\nunless your number is even?",
        "start": 3208.08,
        "duration": 5.97
    },
    {
        "text": "Right now every single time it\nreceives a new prop it's updating.",
        "start": 3214.05,
        "duration": 5.02
    },
    {
        "text": "But say we only wanted to count even\nnumbers, what's some strategy that we",
        "start": 3219.07,
        "duration": 4.07
    },
    {
        "text": "may use in order to skip the\nrendering for odd numbers",
        "start": 3223.14,
        "duration": 3.33
    },
    {
        "text": "and only render on even numbers?",
        "start": 3226.47,
        "duration": 1.59
    },
    {
        "text": "AUDIENCE: You could use\n[INAUDIBLE] before an update.",
        "start": 3234.78,
        "duration": 3.85
    },
    {
        "text": "SPEAKER 1: Yeah, so we have this\nthing called shouldComponentUpdate,",
        "start": 3238.63,
        "duration": 3.38
    },
    {
        "text": "which takes the next props.",
        "start": 3242.01,
        "duration": 1.17
    },
    {
        "text": "And so we have the ability\nto look at the next props",
        "start": 3243.18,
        "duration": 2.19
    },
    {
        "text": "and decide whether or\nnot we want to update,",
        "start": 3245.37,
        "duration": 2.77
    },
    {
        "text": "and if we return false from this\nfunction, the update cycle is over.",
        "start": 3248.14,
        "duration": 3.74
    },
    {
        "text": "It won't render.",
        "start": 3251.88,
        "duration": 2.2
    },
    {
        "text": "And so if in this function we wanted\nto check if that count were odd",
        "start": 3254.08,
        "duration": 6.26
    },
    {
        "text": "we can abort early.",
        "start": 3260.34,
        "duration": 2.05
    },
    {
        "text": "And so let's actually do that.",
        "start": 3262.39,
        "duration": 1.61
    },
    {
        "text": "So let's have this method\ncalled shouldComponentUpdate",
        "start": 3264.0,
        "duration": 5.784
    },
    {
        "text": "and first let's just return false.",
        "start": 3269.784,
        "duration": 1.416
    },
    {
        "text": "Now what's going to happen here?",
        "start": 3273.857,
        "duration": 1.333
    },
    {
        "text": "Nothing.",
        "start": 3277.91,
        "duration": 0.88
    },
    {
        "text": "We can see that it's receiving stuff.",
        "start": 3278.79,
        "duration": 1.74
    },
    {
        "text": "So see down here in the logs\nwe're receiving this thing called",
        "start": 3288.46,
        "duration": 4.94
    },
    {
        "text": "updating every second.",
        "start": 3293.4,
        "duration": 2.83
    },
    {
        "text": "But the UI is just stuck\nat 0, it never updates",
        "start": 3296.23,
        "duration": 2.592
    },
    {
        "text": "and that's because we're saying\nhey, should the component update?",
        "start": 3298.822,
        "duration": 2.708
    },
    {
        "text": "No we shouldn't.",
        "start": 3301.53,
        "duration": 1.59
    },
    {
        "text": "And so React is saying,\nOK, then we're not",
        "start": 3303.12,
        "duration": 1.98
    },
    {
        "text": "going to call this render method\nand nothing changes over here.",
        "start": 3305.1,
        "duration": 3.92
    },
    {
        "text": "And so how may we change this is such\nthat it only counts the even numbers?",
        "start": 3309.02,
        "duration": 5.65
    },
    {
        "text": "Well we can say return, check to see if\nthe next Props.count is divisible by 2.",
        "start": 3319.74,
        "duration": 16.17
    },
    {
        "text": "And, if it returns true, that\nmeans we're an odd number.",
        "start": 3335.91,
        "duration": 11.81
    },
    {
        "text": "But what we want is whether\nwe're an even number.",
        "start": 3347.72,
        "duration": 2.89
    },
    {
        "text": "And so we can actually just say,\noh, return the inverse of this.",
        "start": 3350.61,
        "duration": 3.104
    },
    {
        "text": "And now it's only going to\ncount those even numbers.",
        "start": 3353.714,
        "duration": 2.166
    },
    {
        "text": "Does that make sense?",
        "start": 3361.456,
        "duration": 0.874
    },
    {
        "text": "And so say we wanted to do\nsomething like send a request",
        "start": 3366.4,
        "duration": 4.075
    },
    {
        "text": "or server every single\ntime this UI updated,",
        "start": 3370.475,
        "duration": 5.675
    },
    {
        "text": "we wouldn't really want to\ndo that in the render cycle,",
        "start": 3376.15,
        "duration": 2.31
    },
    {
        "text": "we wouldn't really want to do\nit in shouldComponentUpdate.",
        "start": 3378.46,
        "duration": 4.6
    },
    {
        "text": "We can actually do that\nin ComponentDidUpdate.",
        "start": 3383.06,
        "duration": 2.198
    },
    {
        "text": "And so we can actually do for\nnow let's just console.log.",
        "start": 3388.32,
        "duration": 3.18
    },
    {
        "text": "We can say, hey, we updated it\nand we created a new number.",
        "start": 3397.13,
        "duration": 4.63
    },
    {
        "text": "And as you see, it's only getting\ncalled for those even numbers.",
        "start": 3401.76,
        "duration": 4.4
    },
    {
        "text": "Because first shouldComponentUpdate\ngets called and then",
        "start": 3406.16,
        "duration": 3.81
    },
    {
        "text": "it renders and then\nComponentDidUpdate gets called.",
        "start": 3409.97,
        "duration": 3.05
    },
    {
        "text": "And, since we exit early\non all odd numbers,",
        "start": 3413.02,
        "duration": 3.1
    },
    {
        "text": "only the even numbers will reach the\nrender cycle and ComponentDidUpdate.",
        "start": 3416.12,
        "duration": 4.29
    },
    {
        "text": "And so what you see logged\nare only those even numbers.",
        "start": 3420.41,
        "duration": 2.49
    },
    {
        "text": "So does this concept of updating\nand methods that automatically",
        "start": 3430.21,
        "duration": 5.61
    },
    {
        "text": "get invoked makes sense to everyone?",
        "start": 3435.82,
        "duration": 3.324
    },
    {
        "text": "AUDIENCE: Could you only\ndo this kind of stuff",
        "start": 3439.144,
        "duration": 2.39
    },
    {
        "text": "with [INAUDIBLE] and not\nthe purely functional ones?",
        "start": 3441.534,
        "duration": 2.56
    },
    {
        "text": "SPEAKER 1: Yeah.",
        "start": 3444.094,
        "duration": 0.666
    },
    {
        "text": "So the question was, do these\nmethods exist on the functional ones?",
        "start": 3444.76,
        "duration": 3.93
    },
    {
        "text": "And they don't because, say\nthis functional components",
        "start": 3448.69,
        "duration": 4.2
    },
    {
        "text": "are literally just functions.",
        "start": 3452.89,
        "duration": 2.37
    },
    {
        "text": "They take props and they return a node.",
        "start": 3455.26,
        "duration": 2.07
    },
    {
        "text": "And so since they're functions,\nall they do are get invoked.",
        "start": 3457.33,
        "duration": 3.24
    },
    {
        "text": "You pass them props and\nthen you get a node back.",
        "start": 3460.57,
        "duration": 2.452
    },
    {
        "text": "And in order to have\nthese methods you actually",
        "start": 3463.022,
        "duration": 1.958
    },
    {
        "text": "have to have this\nconcept of an instance.",
        "start": 3464.98,
        "duration": 5.67
    },
    {
        "text": "And so React components have\ninstances, and these instances",
        "start": 3470.65,
        "duration": 3.15
    },
    {
        "text": "are tracked throughout their lifecycle.",
        "start": 3473.8,
        "duration": 1.92
    },
    {
        "text": "And since these are class\ninstances React well",
        "start": 3475.72,
        "duration": 4.59
    },
    {
        "text": "go ahead and invoke\nthose methods for you.",
        "start": 3480.31,
        "duration": 3.54
    },
    {
        "text": "And so the stateless\nfunctional components",
        "start": 3483.85,
        "duration": 2.254
    },
    {
        "text": "are just functions that\nget invoked and do not",
        "start": 3486.104,
        "duration": 1.916
    },
    {
        "text": "have these class methods, whereas\nthe React components not only have",
        "start": 3488.02,
        "duration": 3.96
    },
    {
        "text": "these methods but the methods also\nget invoked automatically for you.",
        "start": 3491.98,
        "duration": 3.14
    },
    {
        "text": "But yeah great question.",
        "start": 3495.12,
        "duration": 1.0
    },
    {
        "text": "So that's the update cycle.",
        "start": 3500.36,
        "duration": 2.43
    },
    {
        "text": "And then lastly we have what's\ncalled the unmount cycle.",
        "start": 3502.79,
        "duration": 3.566
    },
    {
        "text": "There's only one thing that\nhappens in the unmount cycle.",
        "start": 3506.356,
        "duration": 2.374
    },
    {
        "text": "You have componentWillUnmount which\ngives you a chance to clean up.",
        "start": 3508.73,
        "duration": 4.42
    },
    {
        "text": "What do I mean by clean up?",
        "start": 3513.15,
        "duration": 1.13
    },
    {
        "text": "Well, you can remove any event listeners\nif you had them in React, mostly Web.",
        "start": 3514.28,
        "duration": 5.91
    },
    {
        "text": "You can invalidate any network\nrequests that you have out.",
        "start": 3520.19,
        "duration": 2.67
    },
    {
        "text": "Or lastly you should clear\nany timeouts or intervals.",
        "start": 3522.86,
        "duration": 3.0
    },
    {
        "text": "And so there's actually some bugs that\nyou can create if you're not careful.",
        "start": 3525.86,
        "duration": 6.1
    },
    {
        "text": "So let's actually revert\nthis back to being",
        "start": 3531.96,
        "duration": 8.86
    },
    {
        "text": "just an app that shows that count.",
        "start": 3540.82,
        "duration": 6.43
    },
    {
        "text": "So now we have again that\nnumber being incremented.",
        "start": 3555.81,
        "duration": 3.61
    },
    {
        "text": "And this class called app keeps track\nof its own number and is updating.",
        "start": 3567.75,
        "duration": 6.52
    },
    {
        "text": "But say, let's actually\ncall this counter",
        "start": 3574.27,
        "duration": 5.03
    },
    {
        "text": "and create this thing called app.",
        "start": 3579.3,
        "duration": 2.1
    },
    {
        "text": "And in this, let's actually\njust show the component.",
        "start": 3590.59,
        "duration": 2.752
    },
    {
        "text": "So now we have basically\nthe same exact thing.",
        "start": 3615.49,
        "duration": 2.03
    },
    {
        "text": "So we have this thing\ncalled class app which",
        "start": 3617.52,
        "duration": 2.87
    },
    {
        "text": "just returns an instance of counter.",
        "start": 3620.39,
        "duration": 2.54
    },
    {
        "text": "And counter is what we've\nbeen working on thus far.",
        "start": 3622.93,
        "duration": 2.44
    },
    {
        "text": "It creates an interval and we'll\nkeep track of that interval",
        "start": 3625.37,
        "duration": 2.64
    },
    {
        "text": "and keep counting up.",
        "start": 3628.01,
        "duration": 2.21
    },
    {
        "text": "But say we actually have this button\nthat will toggle whether or not",
        "start": 3630.22,
        "duration": 3.79
    },
    {
        "text": "this counter is shown.",
        "start": 3634.01,
        "duration": 1.14
    },
    {
        "text": "And so let's have this\nthing called state",
        "start": 3635.15,
        "duration": 13.81
    },
    {
        "text": "and let's have this\nflag called show counter",
        "start": 3648.96,
        "duration": 3.037
    },
    {
        "text": "and let's initialize it to true.",
        "start": 3651.997,
        "duration": 1.333
    },
    {
        "text": "And then down here we\ncan do something like,",
        "start": 3657.27,
        "duration": 4.8
    },
    {
        "text": "if you should show the\ncounter then return this.",
        "start": 3662.07,
        "duration": 9.25
    },
    {
        "text": "Else let's just return an empty view.",
        "start": 3676.96,
        "duration": 2.356
    },
    {
        "text": "And so now this is basically\nthe exact same thing",
        "start": 3687.75,
        "duration": 2.76
    },
    {
        "text": "because we have no way to change whether\nor not we want to show the counter.",
        "start": 3690.51,
        "duration": 4.65
    },
    {
        "text": "But say we did, so let's\ncreate toggleCounter.",
        "start": 3695.16,
        "duration": 2.61
    },
    {
        "text": "So show counter.",
        "start": 3708.04,
        "duration": 2.17
    },
    {
        "text": "It should be the opposite of what\nthe previous state show counter was.",
        "start": 3710.21,
        "duration": 3.07
    },
    {
        "text": "And let's also have a button\nthat will toggle this counter.",
        "start": 3716.14,
        "duration": 17.34
    },
    {
        "text": "And so now we have a button\nwhere if we click it,",
        "start": 3743.37,
        "duration": 3.582
    },
    {
        "text": "we can just toggle whether\nor not that counter shows.",
        "start": 3746.952,
        "duration": 2.208
    },
    {
        "text": "And there's actually\na pretty bad bug here.",
        "start": 3761.53,
        "duration": 2.726
    },
    {
        "text": "And that is that when we\ntoggled this counter--",
        "start": 3767.61,
        "duration": 3.512
    },
    {
        "text": "oops, we should return this--",
        "start": 3775.59,
        "duration": 3.68
    },
    {
        "text": "when you toggle that counter we\nnever actually tell this component,",
        "start": 3779.27,
        "duration": 6.18
    },
    {
        "text": "hey, stop incrementing.",
        "start": 3785.45,
        "duration": 3.372
    },
    {
        "text": "It's actually going\nto keep incrementing.",
        "start": 3788.822,
        "duration": 1.708
    },
    {
        "text": "And so we can show that if\nwe have here, if we console",
        "start": 3790.53,
        "duration": 2.94
    },
    {
        "text": "that log we see that it's\nincrementing, and if we toggle it,",
        "start": 3793.47,
        "duration": 10.66
    },
    {
        "text": "it's still logging.",
        "start": 3804.13,
        "duration": 1.47
    },
    {
        "text": "So counters now gone.",
        "start": 3805.6,
        "duration": 2.29
    },
    {
        "text": "So there's no counter here, it's\ngone but it keeps saying increment.",
        "start": 3807.89,
        "duration": 6.32
    },
    {
        "text": "And, if we show it again, now look\nat how fast it's incrementing.",
        "start": 3814.21,
        "duration": 10.15
    },
    {
        "text": "It's two every second because\nthe first counter created",
        "start": 3824.36,
        "duration": 5.17
    },
    {
        "text": "an incrementing function every 1,000\nmilliseconds and the second time",
        "start": 3829.53,
        "duration": 4.2
    },
    {
        "text": "we created one it also did.",
        "start": 3833.73,
        "duration": 2.94
    },
    {
        "text": "And so what if we did this again.",
        "start": 3836.67,
        "duration": 1.59
    },
    {
        "text": "Toggle and then toggle again.",
        "start": 3838.26,
        "duration": 3.42
    },
    {
        "text": "Now it's going up three every second.",
        "start": 3841.68,
        "duration": 1.9
    },
    {
        "text": "And if we did this a bunch of times,\nyou see it's going pretty crazy now.",
        "start": 3843.58,
        "duration": 4.67
    },
    {
        "text": "It's like five every second.",
        "start": 3848.25,
        "duration": 2.072
    },
    {
        "text": "And so that's not good.",
        "start": 3850.322,
        "duration": 0.958
    },
    {
        "text": "That's definitely not good at all.",
        "start": 3851.28,
        "duration": 1.99
    },
    {
        "text": "Say you had a super complex app\nand hundreds of timers getting set",
        "start": 3853.27,
        "duration": 4.55
    },
    {
        "text": "and you kept toggling them.",
        "start": 3857.82,
        "duration": 1.53
    },
    {
        "text": "Eventually you're going to have a\nbig problem where a bunch of things",
        "start": 3859.35,
        "duration": 3.03
    },
    {
        "text": "are getting called and nothing\nshould be getting called.",
        "start": 3862.38,
        "duration": 2.91
    },
    {
        "text": "And so that's like a memory leak and\nit could cause your app to crash.",
        "start": 3865.29,
        "duration": 4.35
    },
    {
        "text": "And so how might we\ngo about solving this?",
        "start": 3869.64,
        "duration": 3.61
    },
    {
        "text": "So, as we alluded to, there's\nthis thing called an unmount cycle",
        "start": 3873.25,
        "duration": 3.11
    },
    {
        "text": "where we have a chance to clean up.",
        "start": 3876.36,
        "duration": 2.01
    },
    {
        "text": "We can get rid of any\ntimers that we've created.",
        "start": 3878.37,
        "duration": 5.16
    },
    {
        "text": "And so you can actually do that here.",
        "start": 3883.53,
        "duration": 3.0
    },
    {
        "text": "And so, rather than just\nsetting the interval,",
        "start": 3886.53,
        "duration": 2.22
    },
    {
        "text": "we should actually track that\nfunction that we created.",
        "start": 3888.75,
        "duration": 3.06
    },
    {
        "text": "And so you can do something like\nthis.Interval equals setInterval.",
        "start": 3891.81,
        "duration": 6.18
    },
    {
        "text": "And so setInterval actually returns like\nan ID of the interval that you created.",
        "start": 3897.99,
        "duration": 5.63
    },
    {
        "text": "And so now we're tracking exactly\nthe interval that we created.",
        "start": 3903.62,
        "duration": 4.94
    },
    {
        "text": "And we can go ahead and right\nbefore this component dies,",
        "start": 3908.56,
        "duration": 4.07
    },
    {
        "text": "so component will unmount, we\nshould actually clean that up.",
        "start": 3912.63,
        "duration": 6.84
    },
    {
        "text": "We can actually do clearInterval\nand we pass in that ID.",
        "start": 3919.47,
        "duration": 5.445
    },
    {
        "text": "And so now you can see--",
        "start": 3929.36,
        "duration": 5.07
    },
    {
        "text": "oops, things did not get updated.",
        "start": 3934.43,
        "duration": 3.375
    },
    {
        "text": "Let's actually copy all\nthis and refresh the page.",
        "start": 3937.805,
        "duration": 7.617
    },
    {
        "text": "And so when this loads,\nyou'll see that it will still",
        "start": 3952.06,
        "duration": 4.5
    },
    {
        "text": "log when it's getting shown.",
        "start": 3956.56,
        "duration": 3.49
    },
    {
        "text": "And so as this number is incrementing we\ncan see it saying, oh I'm incrementing.",
        "start": 3960.05,
        "duration": 5.42
    },
    {
        "text": "But when we toggle it that\nnumber no longer goes up.",
        "start": 3965.47,
        "duration": 7.41
    },
    {
        "text": "And then, if we toggle it again,\nit's going to continue incrementing.",
        "start": 3972.88,
        "duration": 4.33
    },
    {
        "text": "And, if we cancel that,\nthat incrementing function",
        "start": 3977.21,
        "duration": 3.74
    },
    {
        "text": "is no longer getting called.",
        "start": 3980.95,
        "duration": 1.76
    },
    {
        "text": "And that's because, over here,\nwhen the component was created,",
        "start": 3982.71,
        "duration": 5.3
    },
    {
        "text": "so when the component mounts, we set\nthe interval for this button increment",
        "start": 3988.01,
        "duration": 5.2
    },
    {
        "text": "to happen every 1,000 seconds.",
        "start": 3993.21,
        "duration": 2.75
    },
    {
        "text": "But then later when we are no\nlonger returning that counter so",
        "start": 3995.96,
        "duration": 8.72
    },
    {
        "text": "the instance gets unmounted.",
        "start": 4004.68,
        "duration": 1.5
    },
    {
        "text": "It's no longer part of the React tree.",
        "start": 4006.18,
        "duration": 1.67
    },
    {
        "text": "Before it gets unmounted, we say\nclear that interval and it clears.",
        "start": 4013.89,
        "duration": 7.21
    },
    {
        "text": "And then when it remounts\nit creates a new interval.",
        "start": 4021.1,
        "duration": 3.38
    },
    {
        "text": "And when it gets unmounted again it\ngoes ahead and clears that interval.",
        "start": 4024.48,
        "duration": 4.47
    },
    {
        "text": "And so now we no longer\nhave any memory leaks.",
        "start": 4028.95,
        "duration": 1.98
    },
    {
        "text": "So does that whole lifecycle\nprocess make sense to people?",
        "start": 4034.76,
        "duration": 3.59
    },
    {
        "text": "Do you have any questions\nabout these methods",
        "start": 4038.35,
        "duration": 2.94
    },
    {
        "text": "or why we might want to use them?",
        "start": 4041.29,
        "duration": 5.78
    },
    {
        "text": "Cool.",
        "start": 4047.07,
        "duration": 0.5
    },
    {
        "text": "Let's take a quick five\nminute break and then",
        "start": 4047.57,
        "duration": 2.36
    },
    {
        "text": "after this, we'll go ahead and\nstart writing some React Native.",
        "start": 4049.93,
        "duration": 2.88
    },
    {
        "text": "Hello and welcome back.",
        "start": 4052.81,
        "duration": 1.38
    },
    {
        "text": "So if you are following Snack some\npeople had some questions about style",
        "start": 4054.19,
        "duration": 5.16
    },
    {
        "text": "and whether or not people\nin industry chose to bundle",
        "start": 4059.35,
        "duration": 2.79
    },
    {
        "text": "this style with each component.",
        "start": 4062.14,
        "duration": 2.46
    },
    {
        "text": "And what I tend to\nsee mostly in industry",
        "start": 4064.6,
        "duration": 2.67
    },
    {
        "text": "is that people do indeed tend to\ninclude the styles with each component",
        "start": 4067.27,
        "duration": 4.5
    },
    {
        "text": "because part of React's\ncomponent mindset",
        "start": 4071.77,
        "duration": 2.64
    },
    {
        "text": "is that each component\nshould be a standalone thing",
        "start": 4074.41,
        "duration": 2.55
    },
    {
        "text": "and it should include with it any event\nhandlers or JavaScript and any style",
        "start": 4076.96,
        "duration": 5.25
    },
    {
        "text": "as well.",
        "start": 4082.21,
        "duration": 1.25
    },
    {
        "text": "But there are many compelling\nreasons to actually remove",
        "start": 4083.46,
        "duration": 3.25
    },
    {
        "text": "the style outside of that component.",
        "start": 4086.71,
        "duration": 1.95
    },
    {
        "text": "And one big compelling reason would\nbe something like color themes.",
        "start": 4088.66,
        "duration": 3.51
    },
    {
        "text": "So say you had some color theme where\nyou really liked crimson in your app",
        "start": 4092.17,
        "duration": 5.91
    },
    {
        "text": "and everywhere you were using crimson.",
        "start": 4098.08,
        "duration": 2.37
    },
    {
        "text": "And then say suddenly you wanted\nto use something like blue.",
        "start": 4100.45,
        "duration": 5.4
    },
    {
        "text": "If you had everything\nhard coded to crimson",
        "start": 4105.85,
        "duration": 2.339
    },
    {
        "text": "it might be a bit of a pain to go\nthrough and find every instance",
        "start": 4108.189,
        "duration": 3.21
    },
    {
        "text": "of that crimson and change it to blue.",
        "start": 4111.399,
        "duration": 1.991
    },
    {
        "text": "But say you actually abstracted\nout some value like primary color",
        "start": 4113.39,
        "duration": 5.299
    },
    {
        "text": "and instead used that in\nall of your components.",
        "start": 4118.689,
        "duration": 2.669
    },
    {
        "text": "Then if you wanted to change the\nprimary color from crimson to blue",
        "start": 4121.358,
        "duration": 2.791
    },
    {
        "text": "it would be very easy.",
        "start": 4124.149,
        "duration": 0.916
    },
    {
        "text": "You would just do it in\none file and be done.",
        "start": 4125.065,
        "duration": 2.265
    },
    {
        "text": "So there are definitely compelling\nreasons to remove the styles out",
        "start": 4127.33,
        "duration": 3.87
    },
    {
        "text": "of a particular component.",
        "start": 4131.2,
        "duration": 2.61
    },
    {
        "text": "And since React Native uses\nJavaScript's objects to style components",
        "start": 4133.81,
        "duration": 4.169
    },
    {
        "text": "it allows you to do stuff like\ncreate variables and import them in.",
        "start": 4137.979,
        "duration": 4.541
    },
    {
        "text": "And so are there reasons\nto take the style sheets",
        "start": 4142.52,
        "duration": 2.75
    },
    {
        "text": "outside of any particular component.",
        "start": 4145.27,
        "duration": 2.549
    },
    {
        "text": "But generally if you\nhave a choice it's easier",
        "start": 4147.819,
        "duration": 2.101
    },
    {
        "text": "to just leave it in there\nfor organization sake.",
        "start": 4149.92,
        "duration": 4.05
    },
    {
        "text": "Cool.",
        "start": 4153.97,
        "duration": 1.36
    },
    {
        "text": "And so up until now we've been writing\na lot of React Native in this browser",
        "start": 4155.33,
        "duration": 6.59
    },
    {
        "text": "environment.",
        "start": 4161.92,
        "duration": 0.78
    },
    {
        "text": "And so let's actually figure out\nand talk about how we actually",
        "start": 4162.7,
        "duration": 3.6
    },
    {
        "text": "write React Native if you were to\nstart your own personal project",
        "start": 4166.3,
        "duration": 4.019
    },
    {
        "text": "or assignment for the course.",
        "start": 4170.319,
        "duration": 3.16
    },
    {
        "text": "So I've been talking about this\ncompany called Expo quite a bit.",
        "start": 4173.479,
        "duration": 3.21
    },
    {
        "text": "And what they do is they create\na very fast way to build an app.",
        "start": 4176.689,
        "duration": 3.46
    },
    {
        "text": "They provide a lot of\ntooling around React",
        "start": 4180.149,
        "duration": 1.75
    },
    {
        "text": "Native and the React native community.",
        "start": 4181.899,
        "duration": 3.302
    },
    {
        "text": "So there are a suite of tools to\naccelerate the React Native development",
        "start": 4185.201,
        "duration": 2.999
    },
    {
        "text": "process.",
        "start": 4188.2,
        "duration": 1.047
    },
    {
        "text": "And so one that we've\nbeen using quite a lot",
        "start": 4189.247,
        "duration": 1.833
    },
    {
        "text": "is this thing called Snack,\nwhich is this website here.",
        "start": 4191.08,
        "duration": 3.81
    },
    {
        "text": "We've used it this course,\na lot this lecture and last.",
        "start": 4194.89,
        "duration": 5.58
    },
    {
        "text": "And what that allows us to do is\nrun React Native in the browser.",
        "start": 4200.47,
        "duration": 3.06
    },
    {
        "text": "So it automatically\nbundles any libraries",
        "start": 4203.53,
        "duration": 2.49
    },
    {
        "text": "that we need like React\nNative, React, and then",
        "start": 4206.02,
        "duration": 3.75
    },
    {
        "text": "it also runs on a phone\nembedded into the browser.",
        "start": 4209.77,
        "duration": 2.55
    },
    {
        "text": "They also give us a tool\ncalled the XDE which",
        "start": 4216.1,
        "duration": 3.03
    },
    {
        "text": "is a GUI, graphical user interface,\nto serve share and publish any Expo",
        "start": 4219.13,
        "duration": 4.8
    },
    {
        "text": "projects that you have.",
        "start": 4223.93,
        "duration": 2.31
    },
    {
        "text": "They also give us a command\nline interface to do",
        "start": 4226.24,
        "duration": 2.04
    },
    {
        "text": "the same things, to be a command line.",
        "start": 4228.28,
        "duration": 3.52
    },
    {
        "text": "They give us the Expo client which,\nif you saw my email from earlier,",
        "start": 4231.8,
        "duration": 4.25
    },
    {
        "text": "is an iPhone app that you can\ninstall and actually run stuff",
        "start": 4236.05,
        "duration": 4.29
    },
    {
        "text": "that you write in Snack or\nstuff that you write and manage",
        "start": 4240.34,
        "duration": 4.29
    },
    {
        "text": "by the XDE or the CLI to actually\nrun it on your phone while developing",
        "start": 4244.63,
        "duration": 5.31
    },
    {
        "text": "and before you publish.",
        "start": 4249.94,
        "duration": 2.61
    },
    {
        "text": "And lastly they give us an\nSDK, software development kit,",
        "start": 4252.55,
        "duration": 3.09
    },
    {
        "text": "which bundles and exposes\ncross-platform libraries and APIs.",
        "start": 4255.64,
        "duration": 3.93
    },
    {
        "text": "And so included in that are maps, stuff\nfor like icons and images and SVGs",
        "start": 4259.57,
        "duration": 8.01
    },
    {
        "text": "and maybe animations.",
        "start": 4267.58,
        "duration": 1.56
    },
    {
        "text": "They also give us handy constants.",
        "start": 4269.14,
        "duration": 1.56
    },
    {
        "text": "So the Expo that we imported into\nthis app is actually the SDK,",
        "start": 4270.7,
        "duration": 5.94
    },
    {
        "text": "and it gave us a constant\nlike, we didn't use it here",
        "start": 4276.64,
        "duration": 4.32
    },
    {
        "text": "but, the height of the status bar.",
        "start": 4280.96,
        "duration": 3.72
    },
    {
        "text": "And so they give us a\nlot of helpful things",
        "start": 4284.68,
        "duration": 2.49
    },
    {
        "text": "to really get our developing\nprocess moving forward.",
        "start": 4287.17,
        "duration": 3.86
    },
    {
        "text": "And so let's take a look at\nthis thing called the XDE.",
        "start": 4291.03,
        "duration": 3.76
    },
    {
        "text": "So I have it here.",
        "start": 4294.79,
        "duration": 1.44
    },
    {
        "text": "It's a little bit small but\nbasically what this is is it",
        "start": 4300.07,
        "duration": 3.9
    },
    {
        "text": "allows us to create and run projects.",
        "start": 4303.97,
        "duration": 2.38
    },
    {
        "text": "And so I actually already created\nthis project before the class,",
        "start": 4306.35,
        "duration": 5.04
    },
    {
        "text": "but when you do create your project\nit allows you to choose a template",
        "start": 4311.39,
        "duration": 4.16
    },
    {
        "text": "and basically create the directory\nand all of its dependencies",
        "start": 4315.55,
        "duration": 5.01
    },
    {
        "text": "on your computer.",
        "start": 4320.56,
        "duration": 1.23
    },
    {
        "text": "And so, if you started with the blank\nlike I did and created my new project,",
        "start": 4321.79,
        "duration": 4.53
    },
    {
        "text": "it gives you a chance to\nsave it wherever you'd like.",
        "start": 4326.32,
        "duration": 7.2
    },
    {
        "text": "But I already went and did that\nprocess and created my new project.",
        "start": 4333.52,
        "duration": 2.97
    },
    {
        "text": "And so, if you want to\nfollow along at home,",
        "start": 4336.49,
        "duration": 2.07
    },
    {
        "text": "you just do create new project,\nblank, save it wherever you like",
        "start": 4338.56,
        "duration": 3.96
    },
    {
        "text": "and then you end up right here.",
        "start": 4342.52,
        "duration": 3.76
    },
    {
        "text": "And basically what this is, is\nthis is running a bunch of things",
        "start": 4346.28,
        "duration": 2.81
    },
    {
        "text": "behind the scenes including React Native\npackager which handles the bundling",
        "start": 4349.09,
        "duration": 3.81
    },
    {
        "text": "and whatnot of your app and any\nlogs if you want to console log,",
        "start": 4352.9,
        "duration": 5.37
    },
    {
        "text": "will also appear in this XDE.",
        "start": 4358.27,
        "duration": 2.31
    },
    {
        "text": "And so what it's doing is it's\nactually looking in that directory",
        "start": 4360.58,
        "duration": 2.97
    },
    {
        "text": "that it created on your computer.",
        "start": 4363.55,
        "duration": 2.278
    },
    {
        "text": "And so if you create it and then CD into\nthe correct directory on your computer",
        "start": 4374.11,
        "duration": 3.78
    },
    {
        "text": "you end up right here.",
        "start": 4377.89,
        "duration": 1.08
    },
    {
        "text": "And so when you create\na new file you see",
        "start": 4381.942,
        "duration": 1.708
    },
    {
        "text": "this thing called app.json\nwhich is basically",
        "start": 4383.65,
        "duration": 5.45
    },
    {
        "text": "a bunch of metadata that's\ncreated about your project and is",
        "start": 4389.1,
        "duration": 2.5
    },
    {
        "text": "how Expo tracks your app.",
        "start": 4391.6,
        "duration": 3.21
    },
    {
        "text": "And then you see this\nthing called app.js.",
        "start": 4394.81,
        "duration": 1.75
    },
    {
        "text": "And that is basically the bare bones\nReact Native app that you start with.",
        "start": 4400.48,
        "duration": 6.92
    },
    {
        "text": "And when you run it, if you open it\nup on a device, you see it run here.",
        "start": 4407.4,
        "duration": 8.106
    },
    {
        "text": "And so this says, open up app.js\nto start working on your app.",
        "start": 4418.86,
        "duration": 3.82
    },
    {
        "text": "And if I were to change the text here\nand save, we can see it re-bundle.",
        "start": 4422.68,
        "duration": 12.88
    },
    {
        "text": "It's currently building\nthat new JavaScript bundle",
        "start": 4435.56,
        "duration": 2.13
    },
    {
        "text": "and then you see here, live on the\nphone, that you did update that text.",
        "start": 4437.69,
        "duration": 5.58
    },
    {
        "text": "And so, if you want to start\nworking on your project earlier",
        "start": 4445.89,
        "duration": 4.31
    },
    {
        "text": "or work on any personal projects of\nyour own, you're welcome to use Expo.",
        "start": 4450.2,
        "duration": 3.48
    },
    {
        "text": "I actually encourage you\nto use Expo because they",
        "start": 4453.68,
        "duration": 2.79
    },
    {
        "text": "take a lot of annoying\nand difficult parts",
        "start": 4456.47,
        "duration": 2.79
    },
    {
        "text": "about creating projects\nand publishing them",
        "start": 4459.26,
        "duration": 1.847
    },
    {
        "text": "and do all the hard work for you\nso that all you have to worry about",
        "start": 4461.107,
        "duration": 2.833
    },
    {
        "text": "is writing the JavaScript here.",
        "start": 4463.94,
        "duration": 1.291
    },
    {
        "text": "Cool.",
        "start": 4470.33,
        "duration": 0.99
    },
    {
        "text": "And so we've been doing this thing a\nlot in this lecture and previous ones",
        "start": 4471.32,
        "duration": 4.089
    },
    {
        "text": "called importing and exporting.",
        "start": 4475.409,
        "duration": 1.291
    },
    {
        "text": "And we haven't actually\ntalked about what is.",
        "start": 4476.7,
        "duration": 2.65
    },
    {
        "text": "And so we have talked\na lot about components",
        "start": 4479.35,
        "duration": 3.1
    },
    {
        "text": "and how we should break up components.",
        "start": 4482.45,
        "duration": 2.372
    },
    {
        "text": "And it's actually also highly encouraged\nthat you break up the components",
        "start": 4484.822,
        "duration": 3.968
    },
    {
        "text": "into their own files.",
        "start": 4488.79,
        "duration": 1.49
    },
    {
        "text": "And so we've seen that components\nare great for simplifying your code",
        "start": 4490.28,
        "duration": 3.234
    },
    {
        "text": "and we can actually split\nthem into their own files.",
        "start": 4493.514,
        "duration": 2.166
    },
    {
        "text": "And then what this allows us to do is\nhelp organize the project even more.",
        "start": 4495.68,
        "duration": 5.19
    },
    {
        "text": "Rather than having everything all\nin one big super long file, which",
        "start": 4500.87,
        "duration": 3.75
    },
    {
        "text": "might get very unwieldy, we\ncan actually organize things",
        "start": 4504.62,
        "duration": 2.46
    },
    {
        "text": "into their own separate files\nor even separate folders",
        "start": 4507.08,
        "duration": 3.57
    },
    {
        "text": "so it's easy to find whatever\ncode you need to update.",
        "start": 4510.65,
        "duration": 3.89
    },
    {
        "text": "Then what we do is from the\nfile that we create we actually",
        "start": 4514.54,
        "duration": 3.37
    },
    {
        "text": "export the component that we want.",
        "start": 4517.91,
        "duration": 2.89
    },
    {
        "text": "And then we can then import it in to\nanother file if we want to use it.",
        "start": 4520.8,
        "duration": 4.82
    },
    {
        "text": "And there are a couple different\nways to import and export.",
        "start": 4527.732,
        "duration": 2.458
    },
    {
        "text": "There's this thing\ncalled a default export,",
        "start": 4530.19,
        "duration": 2.12
    },
    {
        "text": "and there's this thing called\na named import and export.",
        "start": 4532.31,
        "duration": 2.88
    },
    {
        "text": "And so what I was typing a\nlot earlier is you see me type",
        "start": 4535.19,
        "duration": 4.57
    },
    {
        "text": "this thing called export\ndefault class app.",
        "start": 4539.76,
        "duration": 2.62
    },
    {
        "text": "And that's me saying, hey\nfrom this file here I actually",
        "start": 4542.38,
        "duration": 3.43
    },
    {
        "text": "want to export this app.",
        "start": 4545.81,
        "duration": 1.56
    },
    {
        "text": "And it should be the default export.",
        "start": 4547.37,
        "duration": 2.99
    },
    {
        "text": "And so let's take a look\nat what that looks here.",
        "start": 4550.36,
        "duration": 2.23
    },
    {
        "text": "And so in app.js in a brand\nnew directory I went and--",
        "start": 4552.59,
        "duration": 3.99
    },
    {
        "text": "the boiler plate code says\nexport this default class app.",
        "start": 4559.19,
        "duration": 3.0
    },
    {
        "text": "But say I want to in a new file.",
        "start": 4562.19,
        "duration": 2.05
    },
    {
        "text": "So let me create a new file called\nlet's just call it count.js.",
        "start": 4564.24,
        "duration": 4.09
    },
    {
        "text": "From here let's first import from\nReact, which is something that we",
        "start": 4570.95,
        "duration": 6.72
    },
    {
        "text": "have to do in every single file.",
        "start": 4577.67,
        "duration": 2.28
    },
    {
        "text": "And let's create this\ncomponent called Count.",
        "start": 4579.95,
        "duration": 2.91
    },
    {
        "text": "So let's do const Count\nequals props and then",
        "start": 4582.86,
        "duration": 4.2
    },
    {
        "text": "let's return this thing called a view.",
        "start": 4587.06,
        "duration": 2.79
    },
    {
        "text": "And then have props.count show.",
        "start": 4589.85,
        "duration": 5.214
    },
    {
        "text": "Actually, let's have this be text.",
        "start": 4595.064,
        "duration": 1.416
    },
    {
        "text": "So this won't actually work because\nwe're using this component called",
        "start": 4603.81,
        "duration": 4.53
    },
    {
        "text": "Text here which doesn't exist.",
        "start": 4608.34,
        "duration": 3.15
    },
    {
        "text": "So Text here, capital T\ncapital Text, is a component",
        "start": 4611.49,
        "duration": 4.68
    },
    {
        "text": "but this file has no idea what\nText is, what capital Text is.",
        "start": 4616.17,
        "duration": 5.33
    },
    {
        "text": "It's a component.",
        "start": 4621.5,
        "duration": 1.64
    },
    {
        "text": "We know it's a component because\nit's in JSX and capitalized",
        "start": 4623.14,
        "duration": 3.17
    },
    {
        "text": "but nowhere in this file do we\ndeclare this thing called Text.",
        "start": 4626.31,
        "duration": 3.19
    },
    {
        "text": "And so we actually have to import it\nfrom the library called React Native.",
        "start": 4629.5,
        "duration": 4.49
    },
    {
        "text": "And so you've seen me\nbefore in the example",
        "start": 4645.2,
        "duration": 3.33
    },
    {
        "text": "files do this thing called\nimport Text from React Native.",
        "start": 4648.53,
        "duration": 2.71
    },
    {
        "text": "And what that the actually does is it\ngoes into that React Native API code",
        "start": 4651.24,
        "duration": 5.0
    },
    {
        "text": "and gives you access to the variable\nthat they're exporting called Text.",
        "start": 4656.24,
        "duration": 3.79
    },
    {
        "text": "And then when we go\nahead and use it here",
        "start": 4660.03,
        "duration": 3.95
    },
    {
        "text": "the JavaScript knows that\nthis variable context exists.",
        "start": 4663.98,
        "duration": 3.25
    },
    {
        "text": "And so how are we going to get this\ncomponent called Count into our app?",
        "start": 4667.23,
        "duration": 7.43
    },
    {
        "text": "So say I wanted to hear a display\ncount and passed an account of 0.",
        "start": 4677.19,
        "duration": 8.61
    },
    {
        "text": "So if I save this and\ntry to run it, it's",
        "start": 4689.01,
        "duration": 2.37
    },
    {
        "text": "going to error because this\nvariable called Count doesn't exist,",
        "start": 4691.38,
        "duration": 5.29
    },
    {
        "text": "which makes sense right?",
        "start": 4696.67,
        "duration": 2.06
    },
    {
        "text": "In this app.js file we haven't\ncreated a variable called Count.",
        "start": 4698.73,
        "duration": 4.59
    },
    {
        "text": "We actually created it in a\nseparate file called count.js.",
        "start": 4703.32,
        "duration": 5.79
    },
    {
        "text": "And so as I alluded to, you can\nactually export a component from a file",
        "start": 4709.11,
        "duration": 3.6
    },
    {
        "text": "and import it into a new file.",
        "start": 4712.71,
        "duration": 2.03
    },
    {
        "text": "And so we can actually, over here,\njust use this term called export.",
        "start": 4714.74,
        "duration": 4.285
    },
    {
        "text": "And if we go ahead and\nsave this then now we",
        "start": 4723.05,
        "duration": 2.62
    },
    {
        "text": "can try to import this\nthing called Count from--",
        "start": 4725.67,
        "duration": 5.115
    },
    {
        "text": "where is it?",
        "start": 4734.19,
        "duration": 0.636
    },
    {
        "text": "Well, it's in the current\ndirectory, so ./Count.js.",
        "start": 4734.826,
        "duration": 2.124
    },
    {
        "text": "And so now if we save that we\ncan see that it compiles and we",
        "start": 4741.21,
        "duration": 5.85
    },
    {
        "text": "see that 0 show up.",
        "start": 4747.06,
        "duration": 3.39
    },
    {
        "text": "And so let's make it a little bit\nbigger so that's easier to see.",
        "start": 4750.45,
        "duration": 3.74
    },
    {
        "text": "And so how are we going to do that?",
        "start": 4754.19,
        "duration": 1.49
    },
    {
        "text": "Let's create this constant called\nstyles and let's have stylesheet.create.",
        "start": 4755.68,
        "duration": 5.2
    },
    {
        "text": "And let's just have a font size of 72.",
        "start": 4765.51,
        "duration": 5.24
    },
    {
        "text": "And then here let's just do style is\nthat Styles object that we created.",
        "start": 4775.2,
        "duration": 9.931
    },
    {
        "text": "And if we save this and run\nit what's going to happen?",
        "start": 4785.131,
        "duration": 2.249
    },
    {
        "text": "It's going to error.",
        "start": 4787.38,
        "duration": 1.832
    },
    {
        "text": "And why is it erroring?",
        "start": 4789.212,
        "duration": 0.958
    },
    {
        "text": "Well it says cannot find variable called\nstylesheet, which makes sense right?",
        "start": 4790.17,
        "duration": 4.04
    },
    {
        "text": "In this file here nowhere is there\na variable called stylesheet.",
        "start": 4794.21,
        "duration": 5.027
    },
    {
        "text": "And so we actually also have to\nimport that from React Native.",
        "start": 4799.237,
        "duration": 2.583
    },
    {
        "text": "And so if we run that and\nsave it, lo and behold,",
        "start": 4806.19,
        "duration": 2.53
    },
    {
        "text": "it rhymes and the style is applied.",
        "start": 4808.72,
        "duration": 2.29
    },
    {
        "text": "We see a big number 0 there.",
        "start": 4811.01,
        "duration": 3.41
    },
    {
        "text": "And so that is called a named export.",
        "start": 4814.42,
        "duration": 2.13
    },
    {
        "text": "We exported a named\nvariable called Count.",
        "start": 4816.55,
        "duration": 4.56
    },
    {
        "text": "And then in here in brackets we say\nimport all of the variables named Count",
        "start": 4821.11,
        "duration": 6.29
    },
    {
        "text": "that we exported from ./Count.js.",
        "start": 4827.4,
        "duration": 4.48
    },
    {
        "text": "And so that is an example\nof a named export.",
        "start": 4831.88,
        "duration": 1.89
    },
    {
        "text": "And say we wanted to export another\nnamed variable we can do export const--",
        "start": 4833.77,
        "duration": 8.048
    },
    {
        "text": "let's just call it num, and\nlet's have it be the number 50.",
        "start": 4844.954,
        "duration": 6.936
    },
    {
        "text": "And we can, over here, do import\nCount and also num count.js.",
        "start": 4851.89,
        "duration": 5.91
    },
    {
        "text": "And then rather than passing\nin 0 we can just pass in num.",
        "start": 4857.8,
        "duration": 4.58
    },
    {
        "text": "And as we see over here\nnow it's the number 50.",
        "start": 4862.38,
        "duration": 4.13
    },
    {
        "text": "Why is that?",
        "start": 4866.51,
        "duration": 0.69
    },
    {
        "text": "Well in Count.js we\nexported two variables.",
        "start": 4867.2,
        "duration": 5.0
    },
    {
        "text": "One we called Count,\nso capital Count here.",
        "start": 4872.2,
        "duration": 3.75
    },
    {
        "text": "We have a const called Count\nand we're exporting that.",
        "start": 4875.95,
        "duration": 2.65
    },
    {
        "text": "And so it's a named variable\nthat's getting exported.",
        "start": 4878.6,
        "duration": 3.09
    },
    {
        "text": "Over here we have a constant called\nnum, and we're exporting that,",
        "start": 4881.69,
        "duration": 3.42
    },
    {
        "text": "so there's also a named variable\ncalled num that's getting exported.",
        "start": 4885.11,
        "duration": 3.3
    },
    {
        "text": "Then over here in our\napp file we actually",
        "start": 4888.41,
        "duration": 2.4
    },
    {
        "text": "import to this thing\ncalled Count and num.",
        "start": 4890.81,
        "duration": 2.589
    },
    {
        "text": "And so the names do\nmatter because it needs",
        "start": 4893.399,
        "duration": 1.791
    },
    {
        "text": "to know exactly what we're importing in.",
        "start": 4895.19,
        "duration": 2.884
    },
    {
        "text": "And then we go ahead and use those\nand they show up as expected.",
        "start": 4898.074,
        "duration": 2.666
    },
    {
        "text": "And so those are called named\nimports and named exports",
        "start": 4903.57,
        "duration": 3.32
    },
    {
        "text": "but there's also this thing\ncalled a default export.",
        "start": 4906.89,
        "duration": 3.0
    },
    {
        "text": "And so you see here we have an\nadditional term called export default",
        "start": 4909.89,
        "duration": 5.43
    },
    {
        "text": "this value.",
        "start": 4915.32,
        "duration": 1.51
    },
    {
        "text": "And so in our Count file\nover here let's get rid of--",
        "start": 4916.83,
        "duration": 3.55
    },
    {
        "text": "or let's not actually\nget rid of anything",
        "start": 4920.38,
        "duration": 1.75
    },
    {
        "text": "and let's actually do export\ndefault. And then just",
        "start": 4922.13,
        "duration": 5.42
    },
    {
        "text": "give it a value to export.",
        "start": 4927.55,
        "duration": 2.94
    },
    {
        "text": "So export default this\nfunction that we're creating",
        "start": 4930.49,
        "duration": 3.6
    },
    {
        "text": "and if we want to make this more\nobvious what's happening here",
        "start": 4934.09,
        "duration": 3.03
    },
    {
        "text": "we can actually do\nconst Count equals this.",
        "start": 4937.12,
        "duration": 7.26
    },
    {
        "text": "And then we can do export\ndefault Count, which",
        "start": 4944.38,
        "duration": 3.45
    },
    {
        "text": "is saying set the default\nexport of this file to be Count.",
        "start": 4947.83,
        "duration": 3.7
    },
    {
        "text": "And then how are we going to import it?",
        "start": 4953.705,
        "duration": 1.625
    },
    {
        "text": "Well, rather than\nimporting these name things",
        "start": 4955.33,
        "duration": 4.32
    },
    {
        "text": "we just say we want to import\nthis thing from Count.js.",
        "start": 4959.65,
        "duration": 5.19
    },
    {
        "text": "And since we've dropped\nthose brackets we",
        "start": 4964.84,
        "duration": 2.52
    },
    {
        "text": "say just import whatever\nis default exporting.",
        "start": 4967.36,
        "duration": 3.14
    },
    {
        "text": "And we're going to call it here Count.",
        "start": 4970.5,
        "duration": 2.62
    },
    {
        "text": "And so if you notice it works--",
        "start": 4973.12,
        "duration": 3.42
    },
    {
        "text": "oops as long as I save all\nthe files but I never--",
        "start": 4976.54,
        "duration": 9.09
    },
    {
        "text": "let's change this back to 0.",
        "start": 4985.63,
        "duration": 1.17
    },
    {
        "text": "And so now as you notice it is\nshowing that 0 value as expected.",
        "start": 4990.8,
        "duration": 3.485
    },
    {
        "text": "But let's actually call\nthis something else.",
        "start": 4997.29,
        "duration": 2.68
    },
    {
        "text": "So let's call this custom Count.",
        "start": 4999.97,
        "duration": 2.98
    },
    {
        "text": "So even though over here we're\nexporting a variable called",
        "start": 5009.98,
        "duration": 4.92
    },
    {
        "text": "Count, since we're are using\nit as a default export,",
        "start": 5014.9,
        "duration": 4.89
    },
    {
        "text": "we can import the default export in\nthis file and call it whatever you want.",
        "start": 5019.79,
        "duration": 5.54
    },
    {
        "text": "And so we can call it custom Count over\nhere and it still works as expected.",
        "start": 5025.33,
        "duration": 5.06
    },
    {
        "text": "And so the difference between named\nand default exports are that named, 1,",
        "start": 5030.39,
        "duration": 4.67
    },
    {
        "text": "you can export multiple\nof named exports and also",
        "start": 5035.06,
        "duration": 5.4
    },
    {
        "text": "import to multiple named\nexports from a different file.",
        "start": 5040.46,
        "duration": 3.96
    },
    {
        "text": "And they do have to be named exactly\nas they are in the other files.",
        "start": 5044.42,
        "duration": 5.68
    },
    {
        "text": "But when you export\nsomething default you're",
        "start": 5050.1,
        "duration": 2.15
    },
    {
        "text": "limited to only exporting\none which makes sense.",
        "start": 5052.25,
        "duration": 2.52
    },
    {
        "text": "If you exported multiple defaults you\nwouldn't know which one to import.",
        "start": 5054.77,
        "duration": 4.317
    },
    {
        "text": "And then over here, you\ncan call it whatever",
        "start": 5059.087,
        "duration": 1.833
    },
    {
        "text": "you want because it doesn't matter,\nit's just the default export.",
        "start": 5060.92,
        "duration": 5.16
    },
    {
        "text": "And so that's how you're\ngoing to go about starting",
        "start": 5066.08,
        "duration": 2.37
    },
    {
        "text": "to remove components from one long\nfile and move them into separate files.",
        "start": 5068.45,
        "duration": 7.09
    },
    {
        "text": "And so you can also actually import the\nexport default and also named exports.",
        "start": 5075.54,
        "duration": 10.37
    },
    {
        "text": "So here we are exporting a named export\nand we're also having a default export.",
        "start": 5090.33,
        "duration": 7.11
    },
    {
        "text": "And in here we're importing the default\nand we're also importing a named export",
        "start": 5097.44,
        "duration": 7.9
    },
    {
        "text": "and, as you see, that works as well.",
        "start": 5105.34,
        "duration": 2.44
    },
    {
        "text": "And so over here you see that we\nare importing React from React which",
        "start": 5110.72,
        "duration": 5.2
    },
    {
        "text": "is whatever its default export is.",
        "start": 5115.92,
        "duration": 3.57
    },
    {
        "text": "We could also import one\nof its named exports,",
        "start": 5119.49,
        "duration": 5.67
    },
    {
        "text": "and rather than extending\na React.component",
        "start": 5125.16,
        "duration": 2.84
    },
    {
        "text": "we can just extend\ncomponent here because we",
        "start": 5128.0,
        "duration": 4.3
    },
    {
        "text": "went ahead and imported the named\nexport called component from React.",
        "start": 5132.3,
        "duration": 4.74
    },
    {
        "text": "And so that will also work as well.",
        "start": 5137.04,
        "duration": 2.14
    },
    {
        "text": "So any questions on\nimporting and exporting",
        "start": 5143.89,
        "duration": 2.72
    },
    {
        "text": "and how you would go about\nbreaking up particular components",
        "start": 5146.61,
        "duration": 3.66
    },
    {
        "text": "into separate files?",
        "start": 5150.27,
        "duration": 3.04
    },
    {
        "text": "Yeah.",
        "start": 5153.31,
        "duration": 1.0
    },
    {
        "text": "AUDIENCE: You were able to access\nthe components with React.components.",
        "start": 5154.31,
        "duration": 6.5
    },
    {
        "text": "Is that because the component is\n[INAUDIBLE] named export and the value",
        "start": 5160.81,
        "duration": 6.5
    },
    {
        "text": "in the React.components?",
        "start": 5167.31,
        "duration": 2.0
    },
    {
        "text": "SPEAKER 1: Yes exactly.",
        "start": 5169.31,
        "duration": 1.0
    },
    {
        "text": "So the question was, I was\nable to access component",
        "start": 5170.31,
        "duration": 3.83
    },
    {
        "text": "as React.component and\nseparately also as component",
        "start": 5174.14,
        "duration": 7.86
    },
    {
        "text": "and that's because this thing\ncalled component is actually",
        "start": 5182.0,
        "duration": 3.69
    },
    {
        "text": "a property on this React.",
        "start": 5185.69,
        "duration": 4.56
    },
    {
        "text": "And so what React exports is\nboth a default export, which",
        "start": 5190.25,
        "duration": 4.11
    },
    {
        "text": "is this massive thing where one of\nits object keys is called a component",
        "start": 5194.36,
        "duration": 7.29
    },
    {
        "text": "and has the value of the component\nand it's also separately exporting",
        "start": 5201.65,
        "duration": 4.08
    },
    {
        "text": "a named export called component.",
        "start": 5205.73,
        "duration": 1.86
    },
    {
        "text": "And so we can go ahead and either\nimport the default export and do that",
        "start": 5207.59,
        "duration": 4.27
    },
    {
        "text": ".component or we can import the\nnamed component and just use that.",
        "start": 5211.86,
        "duration": 3.61
    },
    {
        "text": "So you're absolutely correct.",
        "start": 5215.47,
        "duration": 1.92
    },
    {
        "text": "Any other questions on\nimporting and exporting?",
        "start": 5221.23,
        "duration": 2.99
    },
    {
        "text": "Cool.",
        "start": 5227.93,
        "duration": 0.5
    },
    {
        "text": "So when we go ahead and\nimport and export components",
        "start": 5228.43,
        "duration": 4.42
    },
    {
        "text": "they can start to get more and more\ncomplex as we pass down more props.",
        "start": 5232.85,
        "duration": 5.26
    },
    {
        "text": "And so how might we go about\nkeeping track of all of these props?",
        "start": 5238.11,
        "duration": 4.22
    },
    {
        "text": "Well React actually has a\nway to help you with that,",
        "start": 5242.33,
        "duration": 3.09
    },
    {
        "text": "and it's called prop types.",
        "start": 5245.42,
        "duration": 2.22
    },
    {
        "text": "And so React can actually validate\nthe types of a given components props",
        "start": 5247.64,
        "duration": 3.9
    },
    {
        "text": "at runtime which is great.",
        "start": 5251.54,
        "duration": 2.59
    },
    {
        "text": "It's a development tool that\nallows you as a developer",
        "start": 5254.13,
        "duration": 3.09
    },
    {
        "text": "to ensure that you're\npassing the props that you",
        "start": 5257.22,
        "duration": 2.0
    },
    {
        "text": "think you're actually passing down.",
        "start": 5259.22,
        "duration": 1.458
    },
    {
        "text": "And so say you're passing\ndown some prop that's a number",
        "start": 5260.678,
        "duration": 3.972
    },
    {
        "text": "but you actually want it as a string.",
        "start": 5264.65,
        "duration": 2.1
    },
    {
        "text": "It's very easy, as your project scales\nup, to kind of get those mixed up",
        "start": 5266.75,
        "duration": 5.512
    },
    {
        "text": "and maybe you pass down\na string when you meant",
        "start": 5272.262,
        "duration": 1.958
    },
    {
        "text": "to pass down a number or vise versa.",
        "start": 5274.22,
        "duration": 3.31
    },
    {
        "text": "And so this thing called PropTypes\nallows you to keep track of that.",
        "start": 5277.53,
        "duration": 4.31
    },
    {
        "text": "And React will actually do this\nautomatically in development mode.",
        "start": 5281.84,
        "duration": 4.75
    },
    {
        "text": "And this is also great because\nit helps document your APIs.",
        "start": 5286.59,
        "duration": 2.78
    },
    {
        "text": "And so I have this very simple\ncomponent over here called Count",
        "start": 5289.37,
        "duration": 8.19
    },
    {
        "text": "and it takes a single prop called Count.",
        "start": 5297.56,
        "duration": 2.16
    },
    {
        "text": "But say it also took\nthree other props and say",
        "start": 5299.72,
        "duration": 2.825
    },
    {
        "text": "it also had 10 other components\nthat also took their own props.",
        "start": 5302.545,
        "duration": 5.365
    },
    {
        "text": "It might get kind of hard to\nremember that as I scale the project.",
        "start": 5307.91,
        "duration": 4.11
    },
    {
        "text": "And say you're somebody\nlike Facebook who",
        "start": 5312.02,
        "duration": 1.8
    },
    {
        "text": "have something like 30,000\ndifferent components in production",
        "start": 5313.82,
        "duration": 3.69
    },
    {
        "text": "it would be very painful to\nnot have those documented",
        "start": 5317.51,
        "duration": 2.21
    },
    {
        "text": "and have to go and read the code to\nknow exactly what props you should",
        "start": 5319.72,
        "duration": 2.98
    },
    {
        "text": "be passing.",
        "start": 5322.7,
        "duration": 1.45
    },
    {
        "text": "And so by declaring this\nthing called PropTypes",
        "start": 5324.15,
        "duration": 3.95
    },
    {
        "text": "you actually can help self\ndocument all of these APIs.",
        "start": 5328.1,
        "duration": 3.59
    },
    {
        "text": "And what's nice is this only\nruns in development mode",
        "start": 5331.69,
        "duration": 2.23
    },
    {
        "text": "and so you don't have to\nworry about it slowing down",
        "start": 5333.92,
        "duration": 2.166
    },
    {
        "text": "your production in production mode.",
        "start": 5336.086,
        "duration": 3.604
    },
    {
        "text": "And so how might we go about doing that?",
        "start": 5339.69,
        "duration": 2.45
    },
    {
        "text": "There's actually a\npackage called PropTypes.",
        "start": 5342.14,
        "duration": 2.07
    },
    {
        "text": "It used to be bundled as\npart of React but they've",
        "start": 5344.21,
        "duration": 2.91
    },
    {
        "text": "since split it into its own\nmodule though it's still",
        "start": 5347.12,
        "duration": 5.73
    },
    {
        "text": "maintained by Facebook.",
        "start": 5352.85,
        "duration": 1.62
    },
    {
        "text": "So we can go ahead and do this\nthing called import PropTypes",
        "start": 5354.47,
        "duration": 4.47
    },
    {
        "text": "from a package called prop-types.",
        "start": 5358.94,
        "duration": 1.95
    },
    {
        "text": "And so now we have access to\nthis variable called PropTypes",
        "start": 5364.97,
        "duration": 2.61
    },
    {
        "text": "where importing the default export\nof whatever this library called",
        "start": 5367.58,
        "duration": 6.36
    },
    {
        "text": "PropTypes is.",
        "start": 5373.94,
        "duration": 1.63
    },
    {
        "text": "And so now we can go ahead\nand use that in our file.",
        "start": 5375.57,
        "duration": 2.21
    },
    {
        "text": "And so let's go ahead and do Count.",
        "start": 5377.78,
        "duration": 4.2
    },
    {
        "text": "And so we created this\nvariable called Count,",
        "start": 5381.98,
        "duration": 3.25
    },
    {
        "text": "which is a function of a\nstateless functional component.",
        "start": 5385.23,
        "duration": 3.78
    },
    {
        "text": "And we can actually attached to\nit a property called propTypes.",
        "start": 5389.01,
        "duration": 6.48
    },
    {
        "text": "Note that it's a lower case p here.",
        "start": 5395.49,
        "duration": 2.3
    },
    {
        "text": "And I can set it equal to an\nobject and the keys of this object",
        "start": 5401.05,
        "duration": 3.33
    },
    {
        "text": "will map to whatever\nprops that I expect.",
        "start": 5404.38,
        "duration": 3.31
    },
    {
        "text": "And so in this case we expect\na single prop called Count.",
        "start": 5407.69,
        "duration": 3.9
    },
    {
        "text": "And so I can say Count should\nbe of what type, well PropTypes.",
        "start": 5411.59,
        "duration": 4.8
    },
    {
        "text": "So capital P here is referring to\nthe library that we just imported.",
        "start": 5416.39,
        "duration": 4.09
    },
    {
        "text": "And we can say we want a\nnumber, and it's required.",
        "start": 5420.48,
        "duration": 4.24
    },
    {
        "text": "And so now we see this warning.",
        "start": 5428.14,
        "duration": 5.49
    },
    {
        "text": "We see, hey, there's a\nfailed prop type here.",
        "start": 5433.63,
        "duration": 4.77
    },
    {
        "text": "The prop count is marked as\nrequired in this component",
        "start": 5438.4,
        "duration": 3.54
    },
    {
        "text": "called Count but it's values undefined.",
        "start": 5441.94,
        "duration": 2.49
    },
    {
        "text": "Why is it undefined?",
        "start": 5444.43,
        "duration": 1.69
    },
    {
        "text": "Well because we're importing\nthis thing called number",
        "start": 5446.12,
        "duration": 3.71
    },
    {
        "text": "and we're passing this thing\ncalled number over here.",
        "start": 5449.83,
        "duration": 2.31
    },
    {
        "text": "But we're not actually exporting\nanything called number in this module.",
        "start": 5452.14,
        "duration": 4.51
    },
    {
        "text": "And say we actually remove\nthat and passed a 0 here.",
        "start": 5456.65,
        "duration": 7.34
    },
    {
        "text": "Now it'll run as expected.",
        "start": 5466.54,
        "duration": 1.71
    },
    {
        "text": "There are no warnings thrown.",
        "start": 5468.25,
        "duration": 2.91
    },
    {
        "text": "And now let's try simulating a mistake\nwhere rather than passing the number 0",
        "start": 5471.16,
        "duration": 5.22
    },
    {
        "text": "we go ahead and pass the string 0.",
        "start": 5476.38,
        "duration": 4.32
    },
    {
        "text": "The app will still work because we're\njust displaying whatever we pass.",
        "start": 5480.7,
        "duration": 4.47
    },
    {
        "text": "But if you notice we\nhave a warning here.",
        "start": 5485.17,
        "duration": 4.11
    },
    {
        "text": "Warning: Failed prop type.",
        "start": 5489.28,
        "duration": 1.29
    },
    {
        "text": "Invalid prop count of type\nstring supplied to count.",
        "start": 5490.57,
        "duration": 3.24
    },
    {
        "text": "We were actually expecting a number.",
        "start": 5493.81,
        "duration": 1.825
    },
    {
        "text": "And so that's actually\nReact's built-in prop type",
        "start": 5495.635,
        "duration": 2.675
    },
    {
        "text": "system which is checking against the\ntypes that we're passing down here.",
        "start": 5498.31,
        "duration": 4.08
    },
    {
        "text": "We say, hey we're expecting\nthis thing as a number",
        "start": 5502.39,
        "duration": 2.92
    },
    {
        "text": "but since we pass a string it will throw\na warning for us just to let us know,",
        "start": 5505.31,
        "duration": 3.635
    },
    {
        "text": "oh by the way I don't know\nif you know this or not,",
        "start": 5508.945,
        "duration": 2.125
    },
    {
        "text": "but you're passing the wrong type down.",
        "start": 5511.07,
        "duration": 2.25
    },
    {
        "text": "And so we can use this thing\ncalled prop types in order",
        "start": 5513.32,
        "duration": 2.39
    },
    {
        "text": "to validate the props that were passed.",
        "start": 5515.71,
        "duration": 5.162
    },
    {
        "text": "And so in stateless\nfunctional components",
        "start": 5520.872,
        "duration": 1.708
    },
    {
        "text": "we actually just add this as a property.",
        "start": 5522.58,
        "duration": 3.33
    },
    {
        "text": "But say this were actually\na class component.",
        "start": 5525.91,
        "duration": 3.81
    },
    {
        "text": "So let's do class Count,\nextends React.component.",
        "start": 5529.72,
        "duration": 12.96
    },
    {
        "text": "And then we have a render\nwhich will just return this.",
        "start": 5542.68,
        "duration": 5.357
    },
    {
        "text": "And let's fix some styling\nso it's easier to read.",
        "start": 5553.35,
        "duration": 2.16
    },
    {
        "text": "So now we have a class component and\nas long as there are no syntax errors--",
        "start": 5560.5,
        "duration": 7.76
    },
    {
        "text": "There's a syntax error\nsomewhere that I don't see.",
        "start": 5571.06,
        "duration": 6.16
    },
    {
        "text": "Does anybody see the syntax error?",
        "start": 5577.22,
        "duration": 1.51
    },
    {
        "text": "Can anybody beat me to it?",
        "start": 5578.73,
        "duration": 1.693
    },
    {
        "text": "AUDIENCE: Is that last a\nparentheses or is that a bracket?",
        "start": 5580.423,
        "duration": 3.099
    },
    {
        "text": "SPEAKER 1: This here is a parentheses.",
        "start": 5583.522,
        "duration": 1.583
    },
    {
        "text": "Oh, yep.",
        "start": 5585.105,
        "duration": 2.595
    },
    {
        "text": "Nice catch.",
        "start": 5587.7,
        "duration": 0.745
    },
    {
        "text": "I owe you some candy.",
        "start": 5588.445,
        "duration": 0.875
    },
    {
        "text": "So now if we go ahead\nand reload this, it",
        "start": 5592.08,
        "duration": 3.3
    },
    {
        "text": "can't find the called props\nbecause class component",
        "start": 5595.38,
        "duration": 6.51
    },
    {
        "text": "is stored as this.props.",
        "start": 5601.89,
        "duration": 2.13
    },
    {
        "text": "And now we can go ahead and\nsee that it is as expected.",
        "start": 5604.02,
        "duration": 3.789
    },
    {
        "text": "We still have that\nfailed prop type message",
        "start": 5607.809,
        "duration": 1.791
    },
    {
        "text": "because we're passing a string rather\nthan a number but it's working.",
        "start": 5609.6,
        "duration": 4.38
    },
    {
        "text": "And so we can go ahead and\nso we create the class here.",
        "start": 5613.98,
        "duration": 3.7
    },
    {
        "text": "And then we go ahead and do\nCount.propTypes here which works.",
        "start": 5617.68,
        "duration": 3.84
    },
    {
        "text": "But generally the way that you\nsee the convention is actually",
        "start": 5621.52,
        "duration": 4.52
    },
    {
        "text": "to use this thing\ncalled a static method.",
        "start": 5626.04,
        "duration": 3.55
    },
    {
        "text": "And so there's actually a static keyword\nwhere you can do static propTypes",
        "start": 5629.59,
        "duration": 5.35
    },
    {
        "text": "equals that object.",
        "start": 5634.94,
        "duration": 1.69
    },
    {
        "text": "So functionally exactly the same, but\nthe convention is to use this thing",
        "start": 5642.09,
        "duration": 5.27
    },
    {
        "text": "called a static method\nor a static property",
        "start": 5647.36,
        "duration": 5.88
    },
    {
        "text": "because it's just the way that\nthe new class index works.",
        "start": 5653.24,
        "duration": 5.53
    },
    {
        "text": "And so it's functionally the same\nas doing count.propTypes down here,",
        "start": 5658.77,
        "duration": 4.57
    },
    {
        "text": "but the convention is just\nto use the newer syntax.",
        "start": 5663.34,
        "duration": 2.125
    },
    {
        "text": "So any questions on PropTypes?",
        "start": 5668.49,
        "duration": 3.38
    },
    {
        "text": "Does everybody see the\nutility of using them?",
        "start": 5671.87,
        "duration": 2.85
    },
    {
        "text": "They've definitely saved me\nmultiple times on personal projects.",
        "start": 5674.72,
        "duration": 2.865
    },
    {
        "text": "And so now, if we've passed the\ncorrect props, there are no warnings.",
        "start": 5683.83,
        "duration": 6.22
    },
    {
        "text": "Great.",
        "start": 5690.05,
        "duration": 0.5
    },
    {
        "text": "And the last concept I wanted to touch\non is just how the heck do I read docs.",
        "start": 5690.55,
        "duration": 5.515
    },
    {
        "text": "Because I can't possibly teach\nyou every single component",
        "start": 5696.065,
        "duration": 2.375
    },
    {
        "text": "that React Native offers.",
        "start": 5698.44,
        "duration": 1.74
    },
    {
        "text": "But they do offer a\nlot of great components",
        "start": 5700.18,
        "duration": 2.34
    },
    {
        "text": "that you may want to use in either\nproject for this class or maybe",
        "start": 5702.52,
        "duration": 3.48
    },
    {
        "text": "a personal project\nthat you're working on.",
        "start": 5706.0,
        "duration": 1.98
    },
    {
        "text": "And so here's basically\nthe steps that I go through",
        "start": 5707.98,
        "duration": 3.15
    },
    {
        "text": "in order to figure out what I should\nuse when working on my own project.",
        "start": 5711.13,
        "duration": 4.09
    },
    {
        "text": "So first have a goal in mind.",
        "start": 5715.22,
        "duration": 1.832
    },
    {
        "text": "You need to know what problem\nyou're trying to solve.",
        "start": 5717.052,
        "duration": 2.208
    },
    {
        "text": "Otherwise reading a bunch\nabout what's offered",
        "start": 5719.26,
        "duration": 2.31
    },
    {
        "text": "doesn't really mean anything to you.",
        "start": 5721.57,
        "duration": 1.86
    },
    {
        "text": "And so say you were doing\nsomething like the TODO app",
        "start": 5723.43,
        "duration": 3.09
    },
    {
        "text": "that we did before the first\nthing that you'll notice",
        "start": 5726.52,
        "duration": 3.6
    },
    {
        "text": "is that there is no input\ntype checkbox in React Native.",
        "start": 5730.12,
        "duration": 3.7
    },
    {
        "text": "And so you have to figure\nout what is my goal here?",
        "start": 5733.82,
        "duration": 2.57
    },
    {
        "text": "Well I want to replace\nwhat used to be a checkbox.",
        "start": 5736.39,
        "duration": 4.91
    },
    {
        "text": "And so your goal in that\nexample would be all right",
        "start": 5741.3,
        "duration": 2.77
    },
    {
        "text": "I need some component that\nbasically just renders a Boolean.",
        "start": 5744.07,
        "duration": 4.62
    },
    {
        "text": "Then just see what the\nlibrary or framework offers.",
        "start": 5748.69,
        "duration": 2.72
    },
    {
        "text": "And so the way I did that was I\njust browsed through the docs.",
        "start": 5751.41,
        "duration": 3.77
    },
    {
        "text": "So they're linked in this presentation.",
        "start": 5755.18,
        "duration": 2.87
    },
    {
        "text": "I'll go ahead and link them in\nthe Resources tab on the website.",
        "start": 5758.05,
        "duration": 3.51
    },
    {
        "text": "But just see exactly what the library\nhas to offer, see what they have,",
        "start": 5761.56,
        "duration": 4.755
    },
    {
        "text": "then find something that\nsolves your problem.",
        "start": 5766.315,
        "duration": 1.875
    },
    {
        "text": "There may be multiple things\nthat solve your problem",
        "start": 5768.19,
        "duration": 2.19
    },
    {
        "text": "but just try to find the thing\nthat best solves your problem.",
        "start": 5770.38,
        "duration": 2.88
    },
    {
        "text": "And so in my case for that\nparticular Boolean switch",
        "start": 5773.26,
        "duration": 3.09
    },
    {
        "text": "I saw that they had something\ncalled a switch that",
        "start": 5776.35,
        "duration": 2.49
    },
    {
        "text": "just renders a Boolean flag that you\ncan just tap and then configure it.",
        "start": 5778.84,
        "duration": 8.43
    },
    {
        "text": "And so the docs will\ntell you exactly what",
        "start": 5787.27,
        "duration": 2.73
    },
    {
        "text": "the API is, how you can configure\nit, what properties you have to set.",
        "start": 5790.0,
        "duration": 3.42
    },
    {
        "text": "And so for switch we had the value\nwhich was either true or false.",
        "start": 5793.42,
        "duration": 4.37
    },
    {
        "text": "And we had on value change which was, I\nbelieve, the name of the prop that gets",
        "start": 5797.79,
        "duration": 4.9
    },
    {
        "text": "called every single time\nyou change that value.",
        "start": 5802.69,
        "duration": 3.31
    },
    {
        "text": "And so it just fit that API\nto whatever you're using.",
        "start": 5806.0,
        "duration": 6.83
    },
    {
        "text": "And then, of course, if you\nhave trouble even then, then",
        "start": 5812.83,
        "duration": 3.06
    },
    {
        "text": "you can turn to the community.",
        "start": 5815.89,
        "duration": 1.83
    },
    {
        "text": "A great thing about React,\nReact Native is the community.",
        "start": 5817.72,
        "duration": 3.584
    },
    {
        "text": "Lots and lots of people use\nReact, lots and lots of people",
        "start": 5821.304,
        "duration": 2.416
    },
    {
        "text": "use React Native and a\nlot of them are experts",
        "start": 5823.72,
        "duration": 3.942
    },
    {
        "text": "who were once beginners themselves.",
        "start": 5827.662,
        "duration": 1.458
    },
    {
        "text": "And everybody remembers when they\nwere first learning React and React",
        "start": 5829.12,
        "duration": 3.23
    },
    {
        "text": "Native there's just a\nlot around and there's",
        "start": 5832.35,
        "duration": 2.38
    },
    {
        "text": "a lot of stuff in the ecosystem.",
        "start": 5834.73,
        "duration": 2.04
    },
    {
        "text": "And the community's really great in\nhelping each other learn what's around",
        "start": 5836.77,
        "duration": 5.13
    },
    {
        "text": "and how to best solve their problems.",
        "start": 5841.9,
        "duration": 1.612
    },
    {
        "text": "And so just ask the question.",
        "start": 5843.512,
        "duration": 1.208
    },
    {
        "text": "You can ask it in Slack\nif you're part of a class.",
        "start": 5844.72,
        "duration": 2.76
    },
    {
        "text": "You can ask it on something like\nStack Overflow or just Google around.",
        "start": 5847.48,
        "duration": 4.299
    },
    {
        "text": "And so if you run into a\nproblem odds are somebody else",
        "start": 5851.779,
        "duration": 2.291
    },
    {
        "text": "has already run into the problem and\nodds are somebody better than you,",
        "start": 5854.07,
        "duration": 4.93
    },
    {
        "text": "better than I have solved that problem.",
        "start": 5859.0,
        "duration": 2.47
    },
    {
        "text": "And you can go ahead\nand use their solution.",
        "start": 5861.47,
        "duration": 3.89
    },
    {
        "text": "And so any time you get stuck\nfeel free to either browse",
        "start": 5865.36,
        "duration": 4.44
    },
    {
        "text": "the documentation yourself or reach\nout to the staff with any questions.",
        "start": 5869.8,
        "duration": 5.82
    },
    {
        "text": "And so, yeah, that's all\nI have for you today.",
        "start": 5875.62,
        "duration": 3.49
    },
    {
        "text": "Good luck starting your project.",
        "start": 5879.11,
        "duration": 1.61
    },
    {
        "text": "It will be released before next Monday.",
        "start": 5880.72,
        "duration": 3.32
    }
]