I volontari di MDN non hanno ancora tradotto questo articolo in Italiano. Unisciti a noi e traducilo tu stesso.
Puoi anche consultare l’articolo in English (US).

The new.target property lets you detect whether a function or constructor was called using the new operator. In constructors and functions instantiated with the new operator, new.target returns a reference to the constructor or function. In normal function calls, new.target is undefined.




The new.target syntax consists of the keyword "new", a dot, and a property name "target". Normally "new." serves as the context for a property access, but here "new." is not really an object. In constructor calls, however, new.target refers to the constructor invoked by new and so "new." becomes a virtual context.

The new.target property is a meta property that is available to all functions. In arrow functions, new.target refers to the new.target of the surrounding function.


new.target in function calls

In normal function calls (as opposed to constructor function calls), new.target is undefined. This lets you detect if 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');

Foo(); // throws "Foo() must be called with new"
new Foo(); // logs "Foo instantiated 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() {

class B extends A { constructor() { super(); } }

var a = new A(); // logs "A"
var b = new B(); // logs "B"

class C { constructor() { console.log(new.target); } }
class D extends C { constructor() { super(); } }
var c = new C(); // logs class C{constructor(){console.log(new.target);}}
var 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, the class definition of D was printed and similarly in case of c, class C was printed


Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Built-in Function Objects' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Built-in Function Objects' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic Support46 (Yes)41 No (Yes) (Yes)
FeatureAndroidChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic Support4646 (Yes)41 No (Yes) (Yes)

See also

Tag del documento e collaboratori

 Hanno collaborato alla realizzazione di questa pagina: fscholz, enderandpeter, jameshkramer, rwaldron, akshayjai1, denimX, nmve, kdex, jpmedley, dzlabs, imconfig
 Ultima modifica di: fscholz,