A prototype inheritance helper

Prototyper.js

Prototyper = {};
Prototyper.create = function (base)  {
  var empty = function () {};
	empty.prototype = base;
	return new empty();
};
Prototyper.xtends = function (parent, instance) {
    instance.prototype = this.create(parent.prototype);
    instance.prototype.constructor = instance;
    instance.prototype.__super__ = parent;
};

var Car = function(){
	console.log("Car construct");
};

Car.prototype.drive = function () {
	console.log("brumm");
};
var myCar = Prototyper.create(Car.prototype);
console.dir(myCar);

// What should work
var FourWheeler = function() {
    this.__super__();
    console.log("FourWheeler construct");
};
Prototyper.xtends(Car, FourWheeler);
FourWheeler.prototype.driveOffroad = function () {
    console.log("FourWheeler driveOffroad");
}

var jeep = new FourWheeler();
jeep.drive(); //brumm
jeep.driveOffroad(); //FourWheeler driveOffroad
console.log(jeep instanceof FourWheeler); // true
console.log(jeep instanceof Car); // true