JavaScriptを卒業してCoffeeScriptで飛躍しよう - 基本などまとめ ref: http://qiita.com/Yama-to/items/a947cfa2565b03ddc9de

coffee

class Fruit
  constructor: (@name) ->
  hello_world: -> alert "Hello #{@name}!"

class Apple extends Fruit
  hello_world: -> super(); alert "...said Bob."

sungold = new Apple "SunGold"
sungold.hello_world()

#=> "Hello SunGold!"
#=> "...said Bob."

js

var Apple, Fruit, sungold,
  extend = function(child, parent) { for (var key in parent) { if (hasProp.call(parent, key)) child[key] = parent[key]; } function ctor() { this.constructor = child; } ctor.prototype = parent.prototype; child.prototype = new ctor(); child.__super__ = parent.prototype; return child; },
  hasProp = {}.hasOwnProperty;

Fruit = (function() {
  function Fruit(name) {
    this.name = name;
  }

  Fruit.prototype.hello_world = function() {
    return alert("Hello " + this.name + "!");
  };

  return Fruit;

})();

Apple = (function(superClass) {
  extend(Apple, superClass);

  function Apple() {
    return Apple.__super__.constructor.apply(this, arguments);
  }

  Apple.prototype.hello_world = function() {
    Apple.__super__.hello_world.call(this);
    return alert("...said Bob.");
  };

  return Apple;

})(Fruit);

sungold = new Apple("SunGold");

sungold.hello_world();