The value null
represents the intentional absence of any object value. It is one of JavaScript's primitive values and is treated as falsy for boolean operations.
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Syntax
null
Description
The value null
is written with a literal: null
. null
is not an identifier for a property of the global object, like undefined
can be. Instead, null
expresses a lack of identification, indicating that a variable points to no object. In APIs, null
is often retrieved in a place where an object can be expected but no object is relevant.
// 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
Examples
Difference between null
and undefined
When checking for null
or undefined
, beware of the differences between equality (==) and identity (===) operators, as the former performs type-conversion.
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 |
---|
ECMAScript (ECMA-262) The definition of 'null value' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
null | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 3 | Opera Full support 3 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.1.100 |
Legend
- Full support
- Full support