null

null is used for representing the intentional absence of an object value and is a primitive value. Unlike undefined, it is not a property of the global object.

It is equal to undefined but not identical to it.

 null == undefined; // true 
 null === undefined; // false

CAREFUL: The typeof null is 'object'.

typeof null; // 'object';

To properly check if a value is null, compare it with the strict equality operator

var a = null;
a === null; // true