The new.target
pseudo-property lets you detect whether a function or constructor was called using the new operator. In constructors and functions invoked using the new operator, new.target
returns a reference to the constructor or function. In normal function calls, new.target
is undefined
.
new.target
Try it
Syntax
new.target
Description
The new.target
syntax consists of the keyword new
, a dot, and the identifier target
. Normally, the left-hand side of the dot is the object on which property access is performed, but here, new
is not an object.
The new.target
pseudo-property is available in all functions.
In class constructors, it refers to the constructed class.
In ordinary functions, it refers to the function itself, assuming it was invoked via the new operator; otherwise new.target
is undefined
.
In arrow functions, new.target
is inherited from the surrounding scope.
Examples
new.target in function calls
In normal function calls (as opposed to constructor function calls), new.target
is undefined
. This lets you detect whether a function was called with new as a constructor.
function Foo() { if (!new.target) { throw 'Foo() must be called with new' } console.log('Foo instantiated with new') } new Foo() // logs "Foo instantiated with new" Foo() // throws "Foo() must be called with new"
new.target in constructors
In class constructors, new.target
refers to the constructor that was directly invoked by new
. This is also the case if the constructor is in a parent class and was delegated from a child constructor.
class A { constructor() { console.log(new.target.name) } } class B extends A { constructor() { super() } } let a = new A() // logs "A" let b = new B() // logs "B" class C { constructor() { console.log(new.target) } } class D extends C { constructor() { super() } } let c = new C() // logs class C{constructor(){console.log(new.target);}} let d = new D() // logs class D extends C{constructor(){super();}}
Thus from the above example of class C
and D
, it seems that new.target
points to the class definition of class which is initialized. For example, when d
was initialized using new D()
, the class definition of D
was printed; and similarly, in case of c
, the class C
was printed.
Specifications
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
new.target |
46
|
13
|
41
|
No
|
33
|
11
|
46
|
46
|
41
|
33
|
11
|
5.0
|
1.0
|
5.0.0
|
See also
© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/new.target