variables

In this module we'll study variables.

Description

Think of a variable as a container. Cup analogies work really well with understanding variables. They store info. We can pour liquid into a cup and change it's value. We can pour two half cups into another cup. We can pour one cup into a bigger cup and then put it into an array of cups.

File Location

You should be located in the following file:

   javascript-library
        └── 0-PreWork
            └── 1-HTML-Basics
            └── 2-CSS-Basics
            └── 3-JavaScript-Basics
                02-variables.js       <----You will be working in this file in this module.

Description

Variables are used to store values. They are containers for values. That's it. Let's keep it that simple for now.

Declarations

First, they must be declared:

    var x;

The name could be anything you want. You could name it spaghetti or football.

Initialized

Then, variables must be initalized:

    x = 5;

Initialization is used for stating what the value of that variable is holding, as well as its type. (More on types later).

Declarations and Initializations

You can also do it all in one statement:

    var theNumberFive = 5;

Variables Demo

Variables Demo

var x = 1;
console.log(x);

Assignment

It is common to assign a value to a variable. Then use that variable to stand for that think: Consider the following:

const feetInMile = 5260;
console.log(feetInMile);

Naming

We can name variables anything we want. This means that there is room for creative writing in software:

var ageOfMyOldestFerret = 40;
var numberOfEggsInOneSitting = 50;

The variables should be sensibly named though, and able to be understood by fellow developers.

Camel Casing

Variable names, in most cases, should be camel cased. This means that the first word is lower case and each consecutive word is upper case. It has humps like a camel. Consider the following examples:

var numberOfGrammysIHaveWon = 0; 
var myBirthYear = 1976;
var newNumber = 1 * numberOfGrammysIHaveWon;

Think it Through

Think through the answer for each one of the problems below:

var age = 40;
var ageInAugust = age + 1;  
console.log(ageInAugust);//What will you get here?

var eleven = 11;
console.log(eleven * eleven); //What will the answer be?

var nineteen = 19;
console.log(age - nineteen); //What will the answer be?

A FEW DON'TS

You can't start a variable with a number:

var 2nite = "Tonight"
//console.log(2nite); //won't work.

Reserved Words

There are exceptions for naming variables. The following list is a group of reserved words in JavaScript, and they should not be used as variable names:

Reserved Word List
abstract	else	instanceof	super
boolean	enum	int	switch
break	export	interface	synchronized
byte	extends	let	this
case	false	long	throw
catch	final	native	throws
char	finally	new	transient
class	float	null	true
const	for	package	try
continue	function	private	typeof
debugger	goto	protected	var
default	if	public	void
delete	implements	return	volatile
do	import	short	while
double	in	static	with