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Variables store information so that it can be used later! Like many other programming languages, JavaScript has variables. JavaScript variables can hold a value of any data type. A variable's value can change during the script.

 

Var name;
Var age;
Var x,y,z;

 

Note: If you try to assign a value to a non-existent variable, JavaScript will create the variable for you.

You can refer to a variable by name to see its value or to change its value. The value type of a variable can change during the execution of a program and JavaScript takes care of it automatically.

Note: JavaScript variable names are case sensitive. And it's better to start with a letter or underscore "_".

 

Variable Scope

Local Variables:

For example parameters of a function is always local to the same function:

 

 function sample( name, family) {
        name = "ehsan";
        family = "ghanbari";
    }

 

 

Global variable:

A global variable has the global scope which means it is defined everywhere in your JavaScript code. Take a look at this example:

 

var culture = "something";                       
function sample( ) {
   base.culture = "base culture";                          
   return null;
}

function sample2() {
   var localVar="this culture";                    
   return null;

}

 

Definitely, the variable in the sample is global (because of base) and the one in sample2 is local.

 

Read more:

1. http://www.tutorialspoint.com/javascript/javascript_variables.htm
2. http://webcheatsheet.com/javascript/variables.php