null
The value nullrepresents the intentional absence of any object value. It is one of JavaScript's primitive values and is treated as falsyfor boolean operations.
Syntax
null
Description
The valuenull is written with aliteral:null. null is not an identifier fora property of the global object, like undefined can be. Instead, nullexpresses alack 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
| ECMAScript Language Specification [ECMAScript] # sec-null-value |
Browser compatibility
BCD tables only load in the browser
See also
- undefined
- NaN
- void operator