Our volunteers haven't translated this article into বাংলা (বাংলাদেশ) yet. Join us and help get the job done!
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 identifer 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 (bug in ECMAScript, should be null) typeof undefined // undefined null === undefined // false null == 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
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |