I notice I can create from a timeline a nice transcription, but it's not the format I need. Any way to create that vtt file with PR? This is what one looks like
WEBVTT
0
00:00:00.870 --> 00:00:03.380
before doing any javascript programming,
1
00:00:03.390 --> 00:00:06.640
you really need to understand some basic fundamentals
2
00:00:06.910 --> 00:00:11.060
that includes the language variables. How to declare them or maybe not
3
00:00:11.190 --> 00:00:15.760
how to work with javascript objects which also includes a raise and
4
00:00:15.760 --> 00:00:21.150
also functions which are at the core of pretty much all javascript functions
5
00:00:21.950 --> 00:00:26.310
just like every other programming language. I know Javascript has variables,
6
00:00:26.570 --> 00:00:28.570
I'm assuming you've used at least one
7
00:00:28.570 --> 00:00:31.090
programming language and when I say variables,
8
00:00:31.100 --> 00:00:32.600
you basically know what I mean.
9
00:00:33.080 --> 00:00:35.920
Some programming languages like basic, for example,
10
00:00:36.060 --> 00:00:38.700
don't require you to declare your variables.
11
00:00:38.790 --> 00:00:42.920
You can just use them directly without any kind of declaration
12
00:00:43.400 --> 00:00:45.840
turns out javascript also lets you do that
13
00:00:45.950 --> 00:00:47.810
but it's a really bad idea.
14
00:00:48.120 --> 00:00:52.940
I don't know of any case, we're just using a variable without first declaring it
15
00:00:53.180 --> 00:00:54.400
makes any sense.
16
00:00:54.750 --> 00:00:58.020
It is a great way though to introduce bugs into your programs.
17
00:00:58.170 --> 00:01:02.220
So I strongly recommend to always declare your variables.
18
00:01:02.520 --> 00:01:04.440
So how do you declare a variable?
19
00:01:04.680 --> 00:01:05.510
It's simple.
20
00:01:05.840 --> 00:01:10.010
Let's go back to our running javascript app, we built in the last module.
21
00:01:10.300 --> 00:01:15.210
I could add one name, my account here to our app. Dot Js javascript file.
22
00:01:15.220 --> 00:01:17.940
We created an in previous module of this course
23
00:01:18.130 --> 00:01:22.270
but there is an easier way for me to demonstrate using javascript variables.
24
00:01:22.700 --> 00:01:26.130
I have not mentioned that javascript is an interpreted language.
25
00:01:26.490 --> 00:01:29.840
We write our code. We run our code and it just works.
26
00:01:30.210 --> 00:01:34.450
That does however, mean that we can type javascript into a command prompt,
27
00:01:34.550 --> 00:01:39.270
basically a javascript interpreter command prompt and we'll get some results
28
00:01:39.570 --> 00:01:41.110
conveniently in our browser.
29
00:01:41.110 --> 00:01:44.180
D bugger we can bring up what we call a console
30
00:01:44.180 --> 00:01:48.590
window and into that we can type javascript commands or statements.
31
00:01:48.900 --> 00:01:49.830
Let's do that
32
00:01:50.410 --> 00:01:55.250
to start in the browser, go to the three dots in the upper right hand corner
33
00:01:55.680 --> 00:01:56.940
click tools,
34
00:01:57.070 --> 00:01:58.640
then developer tools
35
00:01:58.750 --> 00:02:03.230
and that brings up the chrome debug tools at the bottom of our web browser,
36
00:02:04.030 --> 00:02:06.520
click on the console tab and then
37
00:02:06.670 --> 00:02:08.380
the greater than sign showing
38
00:02:08.570 --> 00:02:11.790
is our prompt to type javascript lines of code.
39
00:02:12.520 --> 00:02:15.580
Let's get back to talking about javascript variables. Now
40
00:02:16.230 --> 00:02:18.790
We can declare variables in three ways
41
00:02:19.240 --> 00:02:20.250
we could say
42
00:02:20.680 --> 00:02:21.140
but
43
00:02:21.430 --> 00:02:23.800
my count equals 100
44
00:02:24.480 --> 00:02:25.830
Or we could say
45
00:02:26.230 --> 00:02:29.250
const my count equals 100.
46
00:02:29.850 --> 00:02:32.180
Or even though I hesitate to show you this,
47
00:02:32.610 --> 00:02:36.470
we could say far my account equals 100.
48
00:02:37.210 --> 00:02:39.470
It's probably easiest to save our
49
00:02:39.670 --> 00:02:42.660
because VAR feels like a shortcut for variable
50
00:02:42.980 --> 00:02:43.870
but don't do it.
51
00:02:44.270 --> 00:02:46.720
It's an old syntax and if you use it
52
00:02:46.900 --> 00:02:48.500
people will think you are old
53
00:02:49.130 --> 00:02:50.840
use either letter. Const.
54
00:02:51.560 --> 00:02:55.070
The reason is that by saying let you are declaring
55
00:02:55.080 --> 00:02:58.750
that you plan on updating that variable with the new value
56
00:02:58.880 --> 00:03:00.400
later on in the code.
57
00:03:00.810 --> 00:03:02.180
If you say const
58
00:03:02.310 --> 00:03:05.350
you are saying that this variable will never change
59
00:03:05.540 --> 00:03:09.260
and further you are declaring that if your code does try to change it,
60
00:03:09.440 --> 00:03:11.310
you expect an error to happen.
61
00:03:11.800 --> 00:03:16.710
There's never a reason why you should use VAR in place of let or const
62
00:03:16.980 --> 00:03:18.430
Using letter Const
63
00:03:18.630 --> 00:03:20.760
is just good coding practice
1
Reply
AdChoices