Learning Objective: Learn the three ways to declare variables and understand the rules for naming them.

In earlier versions of JavaScript, variables were solely declared using the var keyword followed by the name of the variable and a semicolon. This is how we would do it.

var variableName = "Old school!";

After ES6 (a newer version of JavaScript) , we now have two new ways to declare a variable: and .

We can take a look at both of them one by one.

• The variable type shares lots of similarities with var but unlike var it has some scope constraints. The scope is out of "scope" of this introductory video but we will explain it in great detail in a later video! The only thing that you need to know right now is that is the preferred way of creating variables in modern JavaScript.

  let mutable = "This can change!";
• is another variable type assigned to data who se value cannot and will not change throught the script. jsx const immutable = 'This cannot change!';

As you can see, I used different names for naming our variables. Everything from , to , and . It can be anything.

But what do you think, do we really have the complete freedom of choosing our variable names? In most cases, yes, you can choose whatever name makes most sense. But there are some quick rules.

Rules for Naming Variables:

1. Names must be unique.
2. Avoid reserved keywords (e.g., is invalid).
3. the first character must be a letter, an underscore (), or a dollar sign (). Subsequent characters may also include numbers.

Try creating some variables yourself!

To recap, there are three different ways to make (or declare) a variable: , and .

From now on, whenever we're creating a new variable, we're going to use either the or the keyword.

when variable is going to be constant and when we plan on changing it!

Let's move on to data types to see what kind of data can we store inside of variables!