Function.prototype.makeCtor: Guarantee Javascript function executes as a constructor.

Function.prototype.makeCtor

Function.prototype.makeCtor = function() {
  function ctor() {
    if (!(this instanceof arguments.callee)) {
      return new (arguments.callee.bind.apply(arguments.callee,Array.prototype.concat.apply([null],arguments)));
    } else {
      that.apply(this,arguments);
    }
  };
  return (Function('var that = this; return '+ctor.toString().replace(ctor.name, this.name))).call(this);
}

var A = (function A(a,b) {
  this.a = a;
  this.b = b;
}).makeCtor();

A.prototype = {
  fizz: 'pop'
};

var B = (function B(a,b) {
  this.a = a;
  this.b = b;
}).makeCtor();

B.prototype = Object.create(A.prototype);
B.prototype.hello = 'world';

var foo = A(1,2);
foo instanceof A; // true
foo.a === 1; // true
foo.b === 2; // true

var bar = new A(1,2);
bar instanceof A; // true
bar.a === 1; // true
bar.b === 2; // true

var baz =  B(3,4);
baz instanceof A; // true
baz instanceof B; // true
baz.hello === 'world'; // true
baz.fizz === 'pop'; // true