Isolating the inheritance part into a function

Let's move the code that takes care of all of the inheritance details from the last example into a reusable extend() function:

function extend(Child, Parent) {
var F = function () {};
F.prototype = Parent.prototype;
Child.prototype = new F();
Child.prototype.constructor = Child;
Child.uber = Parent.prototype;
}

Using this function (or your own custom version of it) helps you keep your code clean with regard to the repetitive inheritance-related tasks. This way you can inherit by simply using:

extend(TwoDShape, Shape);

and

extend(Triangle, TwoDShape);

Let's see a complete example:

// inheritance helper
function extend(Child, Parent) {
var F = function () {};
F.prototype = Parent.prototype;
Child.prototype = new F();
Child.prototype.constructor = Child;
Child.uber = Parent.prototype;
}

// define -> augment
function Shape() {}
Shape.prototype.name = 'Shape';
Shape.prototype.toString = function () {
  return this.constructor.uber
    ? this.constructor...