text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
we can begin to allow our JavaScript | 349.58 | 4.05 |
code to respond to how the user is | 351.38 | 4.29 |
actually interacting with our web page | 353.63 | 3.72 |
to say when the user clicks on a button | 355.67 | 3.56 |
I would like to run this particular | 357.35 | 5.4 |
JavaScript function for example so let's | 359.23 | 5.29 |
go ahead and give that a try I'll go | 362.75 | 3.99 |
ahead and now instead of just saying | 364.52 | 4.86 |
alert hello world let me put this alert | 366.74 | 4.74 |
inside of a function and to create a | 369.38 | 4.17 |
function in JavaScript you just use the | 371.48 | 4.41 |
keyword function followed by the name of | 373.55 | 3.54 |
the function I'll call the function | 375.89 | 3.03 |
hello for example and then in | 377.09 | 3.84 |
parenthesis any inputs that function | 378.92 | 3.75 |
takes this hello function is not going | 380.93 | 3.18 |
to take any input so I'll just use an | 382.67 | 4.53 |
empty set of parentheses and then inside | 384.11 | 5.82 |
of curly braces I include any of the | 387.2 | 5.04 |
code that I want to run in this function | 389.93 | 5.01 |
and so what I've done here now is create | 392.24 | 5.1 |
a function called hello and then inside | 394.94 | 3.87 |
of the curly braces have defined the | 397.34 | 3.06 |
body of the function what code should | 398.81 | 3.93 |
run when I run the hello function and | 400.4 | 4.71 |
what the hello function should do is it | 402.74 | 3.96 |
should display an alert that in this | 405.11 | 4.59 |
case says a hello world so now what I'd | 406.7 | 5.88 |
like to do is get this function to run | 409.7 | 5.46 |
when something happens on the page for | 412.58 | 5.37 |
example when a user clicks on a button | 415.16 | 4.08 |
so to do that the first thing I'll need | 417.95 | 3.69 |
to do is actually create a button so add | 419.24 | 4.56 |
a button that just says like click here | 421.64 | 5.82 |
for example so now if i refresh this | 423.8 | 7.44 |
page i now see that i have hello and I | 427.46 | 5.01 |
also have this button that says click | 431.24 | 3.69 |
here but when I click here like nothing | 432.47 | 3.69 |
happens I'm clicking the click here | 434.93 | 2.46 |
button but it's not changing anything | 436.16 | 3.24 |
because I haven't yet said what should | 437.39 | 4.56 |
happen when the user does click on this | 439.4 | 4.71 |
button and so one way we could do this | 441.95 | 5.1 |
is by adding an attribute to this HTML | 444.11 | 6.66 |
element called unclick what this is | 447.05 | 5.97 |
going to do is it's going to add an on | 450.77 | 3.99 |
click handler to this button it's going | 453.02 | 3.48 |
to say what should happen when the user | 454.76 | 3.96 |
clicks on this button and I'm going to | 456.5 | 4.19 |
set the onclick attribute equal to | 458.72 | 5.13 |
running the function hello and in order | 460.69 | 4.84 |
to run a function in JavaScript just as | 463.85 | 3.42 |
you ran a function with Python you use | 465.53 | 3.81 |
the name of the function followed by a | 467.27 | 3.81 |
set of parentheses to say go ahead and | 469.34 | 3.75 |
actually run this function using this | 471.08 | 3.93 |
parenthesis calls the function another | 473.09 | 3.54 |
word for running the function and the | 475.01 | 2.97 |
fact that there's nothing in between the | 476.63 | 2.82 |
parentheses means we're not providing | 477.98 | 3.63 |
anything as input to the hello function | 479.45 | 3.72 |
though if the hello function did take | 481.61 | 3.6 |
inputs we could certainly add that in | 483.17 | 5.46 |
between the parentheses so now I've tied | 485.21 | 5.31 |
the two pieces of this page together I | 488.63 | 3.69 |
have a button that says click here and | 490.52 | 4.62 |
I've added an onclick handler that says | 492.32 | 4.26 |
that when you click on the button you | 495.14 | 4.05 |
should run the hello function and then | 496.58 | 4.14 |
up above I've defined the hello function | 499.19 | 3.54 |
to say what should the hello function do | 500.72 | 3.93 |
well when the function is called we're | 502.73 | 3.57 |
going to display an alert that in this | 504.65 | 4.56 |
case says hello world so now we should | 506.3 | 6.63 |
be able to refresh the page we still see | 509.21 | 5.22 |
the same thing at least initially where | 512.93 | 2.85 |
it just says hello and a button that | 514.43 | 4.2 |
tells me to click here but now if I go | 515.78 | 3.93 |
ahead and click the button that says | 518.63 | 3.57 |
click here well then I get the alert | 519.71 | 4.74 |
that says this page says hello world I | 522.2 | 4.38 |
can press ok and this event handler is | 524.45 | 3.36 |
always going to work I click the button | 526.58 | 3.24 |
again and I get the alert a second time | 527.81 | 3.24 |
because every time I click the button | 529.82 | 2.94 |
it's going to call the hello function | 531.05 | 3.66 |
again and when I click the hello when | 532.76 | 3.69 |
the hello function runs and it is going | 534.71 | 5.4 |
to display this particular alert so this | 536.45 | 5.85 |
now appears to give us a fair amount of | 540.11 | 4.68 |
power and much as in other programming | 542.3 | 4.35 |
languages languages like Python or other | 544.79 | 3.03 |
languages you might have worked with | 546.65 | 3.39 |
JavaScript has all these same types of | 547.82 | 3.8 |
language features so far | 550.04 | 3.41 |
we've seen datatypes things like a | 551.62 | 3.51 |
string but we also have other data types | 553.45 | 3.33 |
that we'll take a look at soon too we've | 555.13 | 3.48 |
seen functions some functions that are | 556.78 | 3.6 |
built into JavaScript like the alert | 558.61 | 3.66 |
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