new.target

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.

Syntax

new.target

Description

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 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.

Examples

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() {
    console.log(new.target.name);
  }
}

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

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

Specifications

Browser compatibility

See also

• Functions
• Classes
• new
• this