new.target

new.target

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"

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"

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(}}