All language subtitles for 8. Naming and Naming Conventions for Javascript Variables

Hi guys. Welcome back.
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It's Angela from The App Brewery once more.
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So, in the last lesson we looked at the power of variables and how we can easily create them using the
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var keyword.
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Now in this lesson I want to cover some really important points about how you should name your variables
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so that you're in keeping with programming best practice.
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So currently I've still got the Snippets and the Console from the last lesson.
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Now this is a good point to show you that if you want to clear the console because it's getting a bit
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too messy or you're seeing too many messages, then you can simply hold down command and press K on Mac
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and on Windows you can hold down control and press K and this will clear your console.
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But remember this does not clear the information that's been stored inside the browser.
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So, for example, if I write myName again, it will still know that myName has the value of Angela.
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So in order to clear all of the data we're going to have to do a hard clean. We're going to have to empty
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all of our cache and delete all of the data.
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So to do that, on the Mac you can click and hold on the reload page and you will get this menu.
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So you have Normal Reload, Hard Reload, and Empty Cache and Hard Reload.
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So this is kind of like the supersized version of reloading.
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And on a PC you just simply need to right click on the reload button to get that menu.
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And now, if I click that, if I typed myName then it would not know what it is.
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It says it's undefined. It doesn't have a clue what it is.
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So we've managed to successfully clear all of the memory of any data.
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So let's go ahead and delete what's inside our Snippets as well so that we start off with an empty slate.
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And what I want to show you is that there are some rules that govern how you should name your variables.
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Now so far we've been naming our variables myName, or yourName, and that kind of makes sense for the context
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that we've been using it in.
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But actually it doesn't matter what you call your name.
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You could call it any string you like,
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and Javascript really doesn't care.
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But if I ask you what do you think yolsdjsj means, what would you say? If accidentally I've managed
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to actually write a real word in Icelandic, because it's distinctly possible,
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then maybe it'll have a meaning for the Icelandic students out there.
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But for most people this doesn't make any sense.
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And when I try to use it or print it, I mean I can if I remember it exactly the way that I typed it,
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but you can see that this is a really really bad idea.
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So just because Javascript doesn't care doesn't mean that we don't care. We should care a lot, because
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imagine working on the same project as as some guy who likes to call his variables
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kasdkj
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ahsdjk,
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and you have to figure out what all of these things mean. You know, what exactly is Angela?
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Is it, what does it mean,
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right?
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It's kind of like if you only speak English and wǒ zhǐ huì shuō zhōngwén, it would be pretty hard for us
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to be friends or work together,
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right?
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So always give meaningful names to your variables and remember that with great power comes great responsibility,
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or even better,
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remember that the next person who has to look after your code could very well be an axe murderer.
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So there are some common rules that good programmers will follow,
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first of which is, give your variables meaningful names so that anybody can figure out quite easily what
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is the data that's likely to be stored inside it.
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It's like if you had named all of your folders on your desktop untitled folder 1, 2, 3, 4,
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5, 6, then you will be spending hours and hours digging through each of these folders trying to find
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the things that you're looking for.
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And instead if you named it pictures or movies or documents then it would be a lot easier to try and
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figure out what they contain.
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And it's the same story here with variable naming.
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So aside from this, there are certain things that Javascript will not let you do when you're trying to
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name your variables.
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So for example I can't call my variable var because this would be insanely confusing and Javascript
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does not actually allow you to do this.
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You can see that we've got this little error here and it already tells us that we can't structure our code like
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this. But you can, however, have a variable name that contains keywords.
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So, for example, if you called it myvar, that's totally valid, and you can see from the coloring or the
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syntax highlighting, it's already showing you that this is valid, and this color is reserved for keywords.
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Now the other rule is that your variable name cannot begin with a number.
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So, for example, you can't call your variable
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123.
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This is also not allowed.
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However, like keywords, your variable name can contain numbers, so you can call it my123 and that's totally
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cool.
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The next rule is that your variable names can't contain spaces, so it can't be my name = "Angela".
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This makes absolutely no sense because it treats that space as if you're trying to write another different
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bit of code.
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The first word that comes after var and a space is going to be seen as the name of your variable.
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So your variable is called my,
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and so it doesn't know what to do with this extra name thing that you've squeezed in here.
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So no spaces basically.
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And finally the names can only contain letters, numbers, the dollar sign, and an underscore.
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No other symbols are valid for naming a variable.
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So, for example, you can't call your variable my-name.
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This is not valid.
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However, if you wish, you can call it my_name. That is a valid variable name.
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Now finally the last thing that you'll see me do throughout the course is that I will name all of my
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variables using camel casing and this means that I will start out the name with a lowercase word and
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then every subsequent word will be capitalized.
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And this is called camel casing, just as the camel humps are higher than its head, first word is not capitalized,
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and every subsequent one is. And the reason why this is really useful is because you avoid situations like
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TherapistFinder.com, which most people will read as TheRapistFinder.com.
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So make sure that when you're creating your own variables that you're following the same good practice
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that we've listed in this lesson. And in the next lesson there's a quick quiz just to test whether if
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you've remembered and embraced some of these rules regarding variable naming. So I'll see you on the
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next lesson.