Variables

Quick reference

• 00:05 In this video I want to talk about variables.
• 00:07 Now we already looked at variables very quickly in the last video, but
• 00:10 now we can talk about them in a little bit more detail.
• 00:12 So what exactly is a variable?
• 00:14 A variable is just about the most basic thing in any programming language.
• 00:18 I mean, all programming languages have variables.
• 00:20 They're pretty universal.
• 00:21 So think of a variable as a bucket or a box.
• 00:24 You can put things in a variable.
• 00:26 You can put things in a bucket or a box.
• 00:28 It's a container that holds things.
• 00:30 You generally put just one thing in a variable at a time.
• 00:33 You can take that thing out later, do something with it, you can remove it,
• 00:36 add something else in there later on, whatever you want.
• 00:39 So how do we create a variable with JavaScript?
• 00:41 Well let's create our little script tag here.
• 00:45 The first thing we do is we declare the variable.
• 00:47 And we do that by this V-A-R that stands for variable.
• 00:51 And next we just give it a name.
• 00:52 So call it myVariable, whatever you want.
• 00:55 And you've now created a variable.
• 00:58 So you wanna be as descriptive as possible when you name your variable.
• 01:02 And like I said earlier, the convention is to use lowercase Camel Case.
• 01:06 So the first word of your name is lowercase and
• 01:09 then the next word is uppercase.
• 01:11 So like I said, try and be as descriptive as possible.
• 01:13 So if you have a variable that's gonna contain a person's full name for instance.
• 01:17 You might wanna call that one fullName, or something like that.
• 01:23 So, whatever's going to be in there, try to name the variable as that.
• 01:26 That's sort of the convention that most people try and follow.
• 01:29 And that's just so later when you're reading through your code
• 01:32 it seems obvious what each variable is.
• 01:34 So we've declared this variable, now we can assign something to it.
• 01:38 So let's change this to firstName.
• 01:44 So to assign something to a variable we've already looked at we just go
• 01:47 firstName = "John".
• 01:53 Very simple, very straightforward.
• 01:54 Now, this is sort of a two step process.
• 01:56 We declared it first, and then we put something inside of it.
• 02:00 You can do them both at the same time.
• 02:02 You can go var firstName = "John".
• 02:08 Most of the time, you'll do it this way, all at one time.
• 02:12 But there are definitely instances where you'll wanna split it up into two
• 02:15 different things.
• 02:16 Either way, it doesn't really matter which one you do, they both work perfectly well.
• 02:19 So we have declared this and added something to it.
• 02:23 We can also declare it again later on.
• 02:26 We can go var firstName like that.
• 02:31 Now even though we've put John in our variable firstName, we can go ahead and
• 02:35 declare it later on.
• 02:36 And John is still in our variable, right?
• 02:40 We don't actually delete anything by declaring it again.
• 02:42 Now you probably won't ever do this, it's just sort of one of those quirky things
• 02:45 about variables I wanted to mention since we're talking about them.
• 02:48 So what sort of things can you put in a variable?
• 02:50 Well, we've already seen that you could put in strings.
• 02:53 For instance this John right here, that's a string.
• 02:55 Likewise if you put your full name, John Elder, that's a string.
• 02:58 Any sort of text surrounded by quotes is a string.
• 03:01 You can also put numbers in there, so we could do 41, right?
• 03:06 Now that we have a number in this variable, we can do math to that variable.
• 03:09 And we're gonna talk about math later on.
• 03:11 But one thing I want to mention there's a difference between this, and
• 03:16 let's copy this.
• 03:17 And this, well actually let's not copy, let's just do it right here.
• 03:23 So this, it looks like 41 but its actually not 41.
• 03:26 This is no longer a number,
• 03:28 we've turned this into a string by surrounding it in quotation marks.
• 03:31 So we cannot do math to this right now, right?
• 03:35 Because it would be like adding two strings, like apples and oranges,
• 03:38 you can't add those.
• 03:39 A number is not surrounded by quotes, so just another little thing to keep in mind.
• 03:44 So, finally naming variables, variable names are called identifiers,
• 03:47 basically just names, right?
• 03:49 And so like I said, you want them to descriptive.
• 03:51 Names can contain letters, numbers, underscores and dollar signs but not
• 03:56 dashes because JavaScript thinks that's a subtraction sign so you can't do that.
• 04:01 You wanna try and start your variables with a letter.
• 04:04 You can start them with an underscore, like that,
• 04:09 or even a dollar sign, but that's not really done very often.
• 04:14 People just don't do that, that's just the convention.
• 04:16 So there are also some words that you can't use as variable names.
• 04:19 For instance, JavaScript keywords, and we'll talk about those a little bit later.
• 04:22 But like for instance this var, V-A-R.
• 04:25 That's what we use to declare a variable.
• 04:27 You couldn't declare a variable named var, right.
• 04:30 You would get an error if you tried to do that.
• 04:31 And there are a bunch of other words that you can't use that are sort of reserved
• 04:34 for JavaScript.
• 04:35 And you'll learn those as you go along.
• 04:37 And for the most part you're not gonna accidentally use one of those, probably.
• 04:41 But if you do you'll get an error and you'll see that.
• 04:43 So that's variables, very basic, very simple.
• 04:46 And in the next video we'll look at assignment operators.

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