//classical inheritance
  var extend = !function () {
    function Proxy() {}

    return function (Child, Parent, protoProps) {
      Proxy.prototype = Parent.prototype;
      Child.prototype = new Proxy();
      Child.prototype.constructor = Child;

      protoProps = protoProps || {};

      for (var prop in protoProps) {
        if (protoProps.hasOwnProperty(prop)) {
          Child.prototype[prop] = protoProps[prop];
        }
      }
    };
  }();