TUTORIALS

# JavaScript Variables

Variables are "containers" for storing information.

## Do You Remember Algebra From School and college ?

Do you remember algebra from school? x=5, y=6, z=x+y

Do you remember that a letter (like x) could be used to hold a value (like 5), and that you could use the information above to calculate the value of z to be 11?

These letters are called variables, and variables can be used to hold values (x=5) or expressions (z=x+y).

## JavaScript Variables

As with algebra, JavaScript variables are used to hold values or expressions.

A variable can have a short name, like x, or a more descriptive name, like carname.

Rules for JavaScript variable names:

• Variable names are case sensitive (y and Y are two different variables)
• Variable names must begin with a letter or the underscore character

Note: Because JavaScript is case-sensitive, variable names are case-sensitive.

## Example

A variable's value can change during the execution of a script. You can refer to a variable by its name to display or change its value.

This example will show you how

## Declaring (Creating) JavaScript Variables

Creating variables in JavaScript is most often referred to as "declaring" variables.

You can declare JavaScript variables with the var statement:

 var x; var carname;

After the declaration shown above, the variables are empty (they have no values yet).

However, you can also assign values to the variables when you declare them:

 var x=5; var carname="Volvo";

After the execution of the statements above, the variable x will hold the value 5, and carname will hold the value Volvo.

Note: When you assign a text value to a variable, use quotes around the value.

## Assigning Values to Undeclared JavaScript Variables

If you assign values to variables that have not yet been declared, the variables will automatically be declared.

These statements:

 x=5; carname="Volvo";

have the same effect as:

 var x=5; var carname="Volvo";

## Redeclaring JavaScript Variables

If you redeclare a JavaScript variable, it will not lose its original value.

 var x=5; var x;

After the execution of the statements above, the variable x will still have the value of 5. The value of x is not reset (or cleared) when you redeclare it.

## JavaScript Arithmetic

As with algebra, you can do arithmetic operations with JavaScript variables:

 y=x-5; z=y+5;

You will learn more about the operators that can be used in the next chapter of this tutorial.