Statements and Comments

Quick reference

• 00:05 Okay, in this video I wanna talk about statements and comments.
• 00:08 So I mentioned statements earlier and
• 00:10 I mentioned that they always end in semicolons.
• 00:13 So whenever you create some sort of program in JavaScript,
• 00:16 you'll usually use many statements.
• 00:18 Up until now we've been using these short little snippets of JavaScript to do things
• 00:23 and they've all been one short line of code or one statement.
• 00:26 For instance right here one statement, one line of code ends in a semi colon.
• 00:30 But normally you can expect a program to contain many statements.
• 00:34 And they all end in semi colons.
• 00:36 So for instance, just to give you an example here,
• 00:39 if we create a very simple program, and we call it var variable.
• 00:44 We haven't talked about variables.
• 00:45 We'll do that next.
• 00:46 But just kinda follow along here.
• 00:49 Here's a statement, and now we can define each of these,
• 00:52 say John b equals Elder,
• 00:58 c equals JavaScript.
• 01:05 I don't know, ha.
• 01:06 And then we go windows window.alert and then (a), let's say.
• 01:13 Now, this is just calling this a variable.
• 01:16 So, if we save this come back here to console.
• 01:20 Reload this page, boom there it says John right?
• 01:23 If we change this to (c) save it come back and hit reload, now it says JavaScript.
• 01:29 So this a very simple program.
• 01:31 It has 1, 2, 3, 4, 5 lines of code, 5 statements they all end in semicolons.
• 01:37 So the next thing I wanna talk about when it comes to statements is white space and
• 01:41 that is all of these spaces in here.
• 01:43 Now JavaScript for the most part ignores white spaces,
• 01:47 we just sort of use it to make our code more readable and
• 01:50 in fact we can remove all this white space like that and
• 01:55 like that and like that and if we save this come back and hit reload.
• 02:01 Here we get our output.
• 02:01 It says JavaScript.
• 02:03 The program runs exactly the same way that it did before,
• 02:06 there's just no white space.
• 02:08 Now, like I said you're always gonna wanna use white space as much as possible,
• 02:12 because it just makes everything more readable, right?
• 02:15 So white space is a big deal.
• 02:16 So those are a couple of syntax things.
• 02:18 Like I said, we're gonna talk about syntax more as we go along,
• 02:21 you're gonna pick up all these little quirks and rules.
• 02:23 So now I wanna talk about comments.
• 02:25 And comments are important no matter what programming language you use; you always
• 02:30 wanna comment your code, you want well-commented code.
• 02:33 It's just a convention, it's just what everyone wants to see.
• 02:35 For instance this program is very simple, if we come back a month from now and
• 02:40 we look at this code,
• 02:41 we're probably gonna be able to figure out what's going on here, right?
• 02:45 But as you create more complicated programs,
• 02:47 it's not always obvious what they're supposed to do.
• 02:50 And you might work on something for six months and then leave it alone for
• 02:52 a year and come back and you can't remember what's going on, like.
• 02:55 What was I doing there?
• 02:56 What was I trying to do?
• 02:57 Well that's what comments are great for.
• 02:59 You wanna comment your code.
• 03:00 In JavaScript to do a basic comment you just do
• 03:03 two forward slashes just like that.
• 03:04 Now everything after this is commented out.
• 03:07 So this is a comment, and you'll notice it's sort of grayed out.
• 03:11 That means that this won't get executed, this is not actual computer code.
• 03:15 This is just a comment and JavaScript will ignore this.
• 03:18 So in fact if we save it, come back here and
• 03:20 hit reload our program works exactly the same.
• 03:23 If we view our page source we can see there's the comment but
• 03:26 the program ignores it.
• 03:27 It doesn't do anything with it.
• 03:28 So that's very important.
• 03:30 That's one way to do comments.
• 03:31 You can also multiple line comments and that is just forward slash and
• 03:36 this, and now we can say this is a comment,
• 03:42 woohoo, to close this comment we just give it another star and a forward slash,
• 03:48 and you can see as soon as we do that everything else popped back into color and
• 03:52 this stuff remained, commented out, it's all gray.
• 03:56 So sometimes it's important to do multiple line comments and that's how you do it.
• 04:01 So that's comments, pretty simple.
• 04:03 Another way you can do comments on the same line as something, is just
• 04:07 the forward slash on the same line, you can do that, that's this is a comment.
• 04:13 Basically, everything after this slash is commented out, until the next line.
• 04:19 Then when the next line comes, its not commented.
• 04:21 So this is a very common way to comment code.
• 04:24 You want to do it on the same line, you just pop those in there.
• 04:27 So that's comments.
• 04:29 That is, those are statements and the next video we're gonna look at variables.
• 04:33 And that's all for this video.

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