Menu

Variables

Variables are named values and can store any type of JavaScript value.

Here’s how to declare a variable:

EXAMPLE
var x = 100;

And here’s what’s happening in the example above:

  • var is the keyword that tells JavaScript you’re declaring a variable.
  • x is the name of that variable.
  • = is the operator that tells JavaScript a value is coming up next.
  • 100 is the value for the variable to store.

Using variables

After you declare a variable, you can reference it by name elsewhere in your code.

EXAMPLE
var x = 100;
x + 102;
OUTPUT
202


You can even use a variable when declaring other variables.

EXAMPLE
var x = 100;
var y = x + 102;
y;
OUTPUT
202

Reassigning variables

You can give an existing variable a new value at any point after it’s declared.

EXAMPLE
var weather = "rainy";
​weather = "sunny";
weather;
OUTPUT
"sunny"

Naming variables

Variable names are pretty flexible as long as you follow a few rules:

  • Start them with a letter, underscore _, or dollar sign $.
  • After the first letter, you can use numbers, as well as letters, underscores, or dollar signs.
  • Don’t use any of JavaScript’s reserved keywords.

With that in mind, here are valid variable names:

EXAMPLE
var camelCase = "lowercase word, then uppercase";
var dinner2Go = "pizza";
var I_AM_HUNGRY = true;
var _Hello_ = "what a nice greeting"
var $_$ = "money eyes";


And here are some invalid variable names — try to spot what’s wrong with each of them:

EXAMPLE
var total% = 78;
var 2fast2catch = "bold claim";
var function = false;
var class = "easy";


Variable names are case-sensitive, so myVar, MyVar, and myvar are all different variables. But generally, it’s a good practice to avoid naming variables so similarly.

Ready to learn more?

Become a Javascript developer at your own pace!

When you sign up with Pluralsight, you'll immediately have access to thousands of expert courses, paths to guide your learning, tools to measure your skills and hands-on resources like exercise files. Javascript is just the beginning. There’s no limit on what you can learn and you can cancel at any time.