深入理解JavaScript系列（29）：设计模式之装饰者模式详解

function Memory(macbook) {
    this.cost = function () {
        return macbook.cost() + 75;
    };
}

function BlurayDrive(macbook) {
    this.cost = function () {
        return macbook.cost() + 300;
    };
}

function Insurance(macbook) {
    this.cost = function () {
        return macbook.cost() + 250;
    };
}

// 用法
var myMacbook = new Insurance(new BlurayDrive(new Memory(new Macbook())));
console.log(myMacbook.cost());

function AbstractDecorator(decorated) {
    this.performTask = function () {
        decorated.performTask();
    };
}

function ConcreteDecoratorClass(decorated) {
    this.base = AbstractDecorator;
    this.base(decorated);

    decorated.preTask = function () {
        console.log('pre-calling..');
    };

    decorated.postTask = function () {
        console.log('post-calling..');
    };

}

var concrete = new ConcreteClass();
var decorator1 = new ConcreteDecoratorClass(concrete);
var decorator2 = new ConcreteDecoratorClass(decorator1);
decorator2.performTask();

tree.getDecorator = function (deco) {
    tree[deco].prototype = this;
    return new tree[deco];
};

tree.RedBalls = function () {
    this.decorate = function () {
        this.RedBalls.prototype.decorate(); // 第7步：先执行原型（这时候是Angel了）的decorate方法
        console.log('Put on some red balls'); // 第8步 再输出 red
        // 将这2步作为RedBalls的decorate方法
    }
};

tree.BlueBalls = function () {
    this.decorate = function () {
        this.BlueBalls.prototype.decorate(); // 第1步：先执行原型的decorate方法，也就是tree.decorate()
        console.log('Add blue balls'); // 第2步 再输出blue
        // 将这2步作为BlueBalls的decorate方法
    }
};

tree.Angel = function () {
    this.decorate = function () {
        this.Angel.prototype.decorate(); // 第4步：先执行原型（这时候是BlueBalls了）的decorate方法
        console.log('An angel on the top'); // 第5步 再输出angel
        // 将这2步作为Angel的decorate方法
    }
};

tree = tree.getDecorator('BlueBalls'); // 第3步：将BlueBalls对象赋给tree，这时候父原型里的getDecorator依然可用
tree = tree.getDecorator('Angel'); // 第6步：将Angel对象赋给tree，这时候父原型的父原型里的getDecorator依然可用
tree = tree.getDecorator('RedBalls'); // 第9步：将RedBalls对象赋给tree

tree.decorate(); // 第10步：执行RedBalls对象的decorate方法