装饰器在js中的实现, 来自http://chrisincambo.wordpress.com/2008/06/23/decorator-pattern-in-javascript-gof-design-patterns/

decorator2.js

//Class to be decorated
function Coffee(){
    this.cost = function(){
        return 1;
    };
}

//Decorator A
function Milk(coffee){
    this.cost = function(){
        return coffee.cost() + 0.5;
    };
}

//Decorator B
function Whip(coffee){
    this.cost = function(){
        return coffee.cost() + 0.7;
    };
}

//Decorator C
function Sprinkles(coffee){
    this.cost = function(){
        return coffee.cost() + 0.2;
    };
}

//Here's one way of using it
var coffee = new Milk(new Whip(new Sprinkles(new Coffee())));
alert( coffee.cost() );

//Here's another
var coffee = new Coffee();
coffee = new Sprinkles(coffee);
coffee = new Whip(coffee);
coffee = new Milk(coffee);
alert(coffee.cost());