node.js实现的装饰者模式示例

var util = require('util');
var Beverage = function(){
  var description = "Unkown Beverage"
  this.getDescription = function(){
    return description;
  }
}
function Espresso(){
  Beverage.call(this);
  this.description = "Espresso";
}
util.inherits(Espresso, Beverage);
Espresso.prototype.cost = function(){
  return 1.99;
}
function HouseBlend(){
  Beverage.call(this);
  this.description = "House Blend Coffee";
}
util.inherits(HouseBlend, Beverage);
HouseBlend.prototype.cost = function(){
  return .89;
}
function Mocha(beverage){
  this.beverage = beverage;
};
Mocha.prototype.getDescription = function(){
  return this.beverage.getDescription() + ", Mocha";
}
Mocha.prototype.cost = function(){
  return 0.20 + this.beverage.cost();
}
function Whip(beverage){
  this.beverage = beverage;
};
Whip.prototype.getDescription = function(){
  return this.beverage.getDescription() + ", Whip";
}
Whip.prototype.cost = function(){
  return 0.40 + this.beverage.cost();
}
var beverage = new Espresso();
console.log(beverage.getDescription() + " $" + beverage.cost());
var beverage2 = new HouseBlend();
beverage2 = new Mocha(beverage2);
beverage2 = new Mocha(beverage2);
beverage2 = new Whip(beverage2);
console.log(beverage2.getDescription() + " $" + beverage2.cost());