null
Thenullvalue represents the intentional absence of any object value. It
is one of JavaScript'sprimitive valuesand
is treated asfalsyfor boolean operations.
Try it
Syntax
js
null
Description
The valuenullis written with a literal:null.
nullis not an identifier for a property of the global object, like
undefinedcan be. Instead,
nullexpresses a lack of identification, indicating that a variable points
to no object. In APIs,nullis often retrieved in a place where an object
can be expected but no object is relevant.
js
// foo does not exist. It is not defined and has never been initialized:
foo;//ReferenceError: foo is not defined
js
// foo is known to exist now but it has no type or value:
constfoo=null;
foo;//null
Examples
Difference betweennullandundefined
When checking fornullorundefined,beware of thedifferences between equality (==) and identity (===) operators,as the former performs
type-conversion.
js
typeofnull;// "object" (not "null" for legacy reasons)
typeofundefined;// "undefined"
null===undefined;// false
null==undefined;// true
null===null;// true
null==null;// true
!null;// true
Number.isNaN(1+null);// false
Number.isNaN(1+undefined);// true
Specifications
| Specification |
|---|
| ECMAScript Language Specification #sec-null-value |
Browser compatibility
BCD tables only load in the browser