gistfile1.js

function Bit(a, b) {
  this.a = a;
  this.b = b;
}

function construct() {
  var args = Array.prototype.splice.call(arguments, 0);
  var fn = args.shift();
  
  function F() {
    return fn.apply(this, args);
  }
  
  F.prototype = constructor.prototype;
  
  return new F();
}

var one = new Bit(1, 2);
var two = construct(Bit, 1, 2);