null

The value null represents the intentional absence of any object value. It is one of JavaScript's primitive values.

Syntax

null 

Description

The value null is written with a literal, null (it's not an identifier for a property of the global object like undefined can be). In APIs, null is often retrieved in place where an object can be expected but no object is relevant. When checking for null or undefined beware of the differences between equality (==) and identity (===) operators (type-conversion is performed with the former).

// foo does not exist. It is not defined and has never been initialized:
> foo
"ReferenceError: foo is not defined"

// foo is known to exist now but it has no type or value:
> var foo = null; foo;
"null"

Difference between null and undefined

typeof null        // "object" (not "null" for legacy reasons)
typeof undefined   // "undefined"
null === undefined // false
null  == undefined // true
null === null //true
null == null //true
!null // true
isNaN(1 + null) //false
isNaN(1 + undefined) //true

Specifications

Specification	Status	Comment
ECMAScript 1st Edition (ECMA-262)	Standard	Initial definition.
ECMAScript 5.1 (ECMA-262) The definition of 'null value' in that specification.	Standard
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'null value' in that specification.	Standard
ECMAScript 2017 Draft (ECMA-262) The definition of 'null value' in that specification.	Draft

Browser compatibility

See also

• undefined
• NaN