text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
particular notation for functions called | 3,691.38 | 3.87 |
the arrow notation for functions and | 3,693.42 | 3.18 |
I'll just show it to you because it'll | 3,695.25 | 3.45 |
come up but often times instead of using | 3,696.6 | 3.93 |
the keyword function before introducing | 3,698.7 | 3.72 |
a function you'll just have something | 3,700.53 | 6.63 |
like button and then arrow the curly | 3,702.42 | 6.12 |
braces and strictly speaking you don't | 3,707.16 | 2.67 |
even need the parentheses around the | 3,708.54 | 3.99 |
input where button arrow and then in | 3,709.83 | 4.74 |
these curly braces some code just means | 3,712.53 | 3.48 |
here is going to be a function that | 3,714.57 | 3.63 |
takes as input a variable called button | 3,716.01 | 5.16 |
and then runs this particular block of | 3,718.2 | 5.16 |
code when that function is run and | 3,721.17 | 4.23 |
likewise if a function takes no input | 3,723.36 | 3.75 |
like this function up here you could | 3,725.4 | 3.6 |
express it using arrow notation with | 3,727.11 | 5.37 |
just parentheses a arrow block and so | 3,729 | 5.16 |
this is often a notation that you'll see | 3,732.48 | 3.57 |
in Java scripts if you ever see it know | 3,734.16 | 3.33 |
that that's really just shorthand for | 3,736.05 | 3.09 |
creating a function whatever is to the | 3,737.49 | 3.75 |
left of the arrow sign is the input to | 3,739.14 | 3.66 |
the function and whatever is to the | 3,741.24 | 3.3 |
right of the arrow is what code should | 3,742.8 | 3.9 |
actually run when the function body gets | 3,744.54 | 4.05 |
executed when the function is called | 3,746.7 | 4.53 |
upon so what other changes might we want | 3,748.59 | 5.13 |
to make two colors dot HTML well if we | 3,751.23 | 4.41 |
look back at colors dot HTML here's what | 3,753.72 | 3.21 |
it looks like now we've got a heading | 3,755.64 | 2.78 |
that says hello and then | 3,756.93 | 3.439 |
to change the color to red or blue or | 3,758.42 | 4.439 |
green for example we might instead if we | 3,760.369 | 4.381 |
want the user to choose from one from a | 3,762.859 | 3.901 |
number of options decide upon the user | 3,764.75 | 4.349 |
interface choice of using a drop-down | 3,766.76 | 3.809 |
instead of a bunch of buttons for | 3,769.099 | 3.45 |
example and JavaScript supports that as | 3,770.569 | 3.061 |
well and we'll use this as an | 3,772.549 | 2.911 |
opportunity to explore some of the other | 3,773.63 | 3.719 |
event handlers that exist within | 3,775.46 | 5.19 |
JavaScript so for example instead of | 3,777.349 | 5.52 |
having these all inside of buttons I can | 3,780.65 | 3.87 |
make my life a little bit easier by | 3,782.869 | 4.351 |
making this a select drop-down where the | 3,784.52 | 4.829 |
Select is going to have an option whose | 3,787.22 | 4.139 |
value is I'll say black is the default | 3,789.349 | 3.99 |
option and I'll say black and then we'll | 3,791.359 | 3.871 |
add another option whose value is red | 3,793.339 | 4.591 |
and then we say red and the value is | 3,795.23 | 4.41 |
what we'll get in JavaScript when we try | 3,797.93 | 3.149 |
and extract the value of a particular | 3,799.64 | 3.719 |
select drop-down well it's in between | 3,801.079 | 4.201 |
the option tags themselves is what the | 3,803.359 | 3.631 |
user is going to see on the page when | 3,805.28 | 2.7 |
they actually view it so I'm | 3,806.99 | 3.569 |
capitalizing it just for them option | 3,807.98 | 4.139 |
value equals blue | 3,810.559 | 3.841 |
that'll be blue and then option value | 3,812.119 | 5.43 |
equals green and that'll be green so now | 3,814.4 | 5.429 |
what the user sees is they see hello and | 3,817.549 | 3.78 |
then a drop-down menu where they can | 3,819.829 | 3.54 |
choose from a list of colors rather than | 3,821.329 | 4.5 |
click buttons in order to do so and now | 3,823.369 | 4.44 |
of course this select drop-down doesn't | 3,825.829 | 3.661 |
do anything at the moment but I can | 3,827.809 | 4.591 |
modify it so that it does so now instead | 3,829.49 | 4.92 |
of selecting for all of the buttons and | 3,832.4 | 3.54 |
doing something with all the buttons we | 3,834.41 | 3.419 |
don't have any buttons anymore what I do | 3,835.94 | 6.75 |
have is I have a select drop-down and | 3,837.829 | 7.411 |
now just as we've seen like on click to | 3,842.69 | 3.96 |
say when you click on something as we've | 3,845.24 | 3.089 |
seen Dom content loaded as an event | 3,846.65 | 4.11 |
there's another event called on change | 3,848.329 | 4.111 |
which applies to things like select | 3,850.76 | 4.26 |
dropdowns where when something changes | 3,852.44 | 3.899 |
in the select drop-down when a user | 3,855.02 | 2.64 |
chooses something different | 3,856.339 | 4.23 |
I can run some code for example so I can | 3,857.66 | 5.1 |
run a function that in this case is | 3,860.569 | 4.55 |
going to take document query selector | 3,862.76 | 3.599 |
hello | 3,865.119 | 3.48 |
meaning get me the hello HTML element | 3,866.359 | 4.861 |
change its style what part of the style | 3,868.599 | 4.96 |
changed its color and I want to change | 3,871.22 | 3.66 |
it to something I want to change it to | 3,873.559 | 5.04 |
the value of this select drop-down but | 3,874.88 | 5.16 |
how do I get access to this particular | 3,878.599 | 4.171 |
select drop-down well in JavaScript we | 3,880.04 | 4.95 |
have access to a special value called | 3,882.77 | 5.64 |
this and this has special meaning in | 3,884.99 | 5.01 |
JavaScript and its meaning varies based | 3,888.41 | 3.84 |
on context but in the context of an | 3,890 | 3.96 |
event handler a function that is called | 3,892.25 | 4.29 |
when a particular event happens this is | 3,893.96 | 4.47 |
going to be a special keyword that | 3,896.54 | 4.32 |
always refers to the thing that received | 3,898.43 | 3.3 |
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