JavaScript 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.

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Correct JavaScript variables

1. var x = 10;  
2. var _value="sonoo";  

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Incorrect JavaScript variables

1. var  123=30;  
2. var *aa=320;  

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Example of JavaScript variable

Let’s see a simple example of JavaScript variable.

1. <script>  
2. var x = 10;  
3. var y = 20;  
4. var z=x+y;  
5. document.write(z);  
6. </script>  

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