decorator.js

var Crepe = function() {
  this.cost     = function() { return 200; };
  this.toppings = function() { return []; };
};

var Topping = function(crepe) {};
Topping.prototype = {
  cost: function () {
    return this.crepe.cost() + this.settings.cost;
  },
  toppings: function() {
     var toppings = this.crepe.toppings();
     toppings.push(this.settings.topping);
     return toppings;
  }
};

var ChocolateTopping = function(crepe) {
  this.crepe = crepe;
  this.settings = {cost: 50, topping: 'chocolate'};
};
ChocolateTopping.prototype = Topping.prototype;

var BananaTopping = function(crepe) {
  this.crepe = crepe;
  this.settings = {cost: 80, topping: 'banana'};
};
BananaTopping.prototype = Topping.prototype;



var plain = new Crepe();
var favoriteCrepe = new BananaTopping(new ChocolateTopping(plain));


// plain crepe
console.log(plain.cost());
console.log(plain.toppings());

// banana chocolate
console.log(favoriteCrepe.cost());
console.log(favoriteCrepe.toppings());