What datatypes are supported in Javascript?

Question

When would you use them?

Answer 1

There are
- Numbers
- Strings
- Booleans
- Objects
- null
- undefined

Note that there isn't a separate Integer, just number - which is represented as a double precision floating point number.

There's also
- Functions
- Arrays
- RegExps

all of which are Objects deep down, but with enough special wiring to be mentioned on their own.

Credit: Stackoverflow

Answer 2

JavaScript has dynamic types. This means that the same variable can be used as different types:

var x;               // Now x is undefined
var x = 5;           // Now x is a Number
var x = "John";      // Now x is a String
var x = true;        // Now x is a Boolean 

However Javascript Array and Object does not apply to the above rule which are descried blow.

Arrays

var cars=new Array();
cars[0]="BMW";
cars[1]="Merc";
or 
var cars=new Array("BMW","Merc");

Objects

var person={firstname:"Salil", lastname:"Agrawal"};