old

Make the 'new' keyword optional for ES6 classes

Usage

npm install old

var old = require('old')
 
class Class {
  // ...
}
 
var Class2 = old(Class)
 
Class() // throws error
Class2() // creates an instance of Class

Rationale

With ES5 "constructor" functions, a common pattern is to make the new keyword optional by doing something like the following:

function Foo () {
  if (!(this instanceof Foo)) return new Foo()
  // do constructor stuff
}

Recently, ES6 introduced classes to replace constructor functions. However, if these classes are instantiated without new, an error is thrown: TypeError: Class constructor Foo cannot be invoked without 'new'. This module makes new optional, even for these ES6 classes.

Credit

• Thank you to Sorella in ##javascript (Freenode) for the clean solution
• Thanks to slikts in ##javascript for the name idea