JS Class Style Inheriting

gistfile1.js

function inherit(pThis, pBase) {
  pThis.prototype = Object.create(pBase.prototype);
  pThis.prototype.constructor = pThis;
  pThis.prototype.super = pBase.prototype;
}

function Animal() {
  this.type = 'animal';
  this.num = 34;
}

Animal.prototype.what = function() {
  return this.type;
}

function Dog() {
  this.super.constructor();
  this.type = 'dog';
}

inherit(Dog, Animal);

function Mut() {
  this.super.constructor();
  this.type = 'Mut';
}

inherit(Mut, Dog);

var mut = new Mut();
mut.num;
> 34
mut.what();
> 'Mut'

mut.super.what();
> 'dog'

mut.super.num
> 34

mut.super.super.what();
> 'animal'

mut.num = 55;

mut.super.num;
> 34

mut.num;
> 55

mut.super.super.num = 126;

mut.num;
> 55

mut.super.num;
> 126 // 設定していないからsuperの値を使った。

mut.super.super.num;
> 126

var mut2 = new Mut();

mut2.num;
> 34

mut2.super.super.num;
> 34 // ちゃんとリセットした