Javascript

Javascript Variable

JavaScript Variable

  1. JavaScript variable
  2. JavaScript Local variable
  3. JavaScript Global variable

A JavaScript variable is simply a name of storage location. There are two types of variables in JavaScript : local variable and global variable.

There are some rules while declaring a JavaScript variable (also known as identifiers).

  1. Name must start with a letter (a to z or A to Z), underscore( _ ), or dollar( $ ) sign.
  2. After first letter we can use digits (0 to 9), for example value1.
  3. JavaScript variables are case sensitive, for example x and X are different variables.

Correct JavaScript variables

 var x = 10;

 var _value="sonoo";

Incorrect JavaScript variables

 var  123=30;

var *aa=320;

Example of JavaScript variable

Let’s see a simple example of JavaScript variable.

 <script>

var x = 10;

var y = 20;

var z=x+y;

document.write(z);

</script>

Output of the above example

example1

 

JavaScript local variable

A JavaScript local variable is declared inside block or function. It is accessible within the function or block only. For example:

 <script>

function abc(){

var x=10;//local variable

}

</script>

Or,

 <script>

If(10<13){

var y=20;//JavaScript local variable

}

</script>

JavaScript global variable

A JavaScript global variable is accessible from any function. A variable i.e. declared outside the function or declared with window object is known as global variable. For example:

 <script>

var data=200;//gloabal variable

function a(){

document.writeln(data);

}

function b(){

document.writeln(data);

}

a();//calling JavaScript function

b();

</script>
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