装饰者模式

1.

//需要装饰的类（函数）
function Macbook() {
    this.cost = function () {
        return 1000;
    };
}

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());

2.

function ConcreteClass() {
    this.performTask = function () {
        this.preTask();
        console.log('doing something');
        this.postTask();
    };
}

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();

3.

var tree = {};
tree.decorate = function () {
    console.log('Make sure the tree won\'t fall');
};

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

4.

/* The Bicycle interface. */

var Bicycle = new Interface('Bicycle', ['assemble', 'wash', 'ride', 'repair', 
    'getPrice']);

/* The AcmeComfortCruiser class. */

var AcmeComfortCruiser = function() { // implements Bicycle
  ...
};
AcmeComfortCruiser.prototype = {
  assemble: function() {
    ...
  },
  wash: function() {
    ...
  },
  ride: function() {
    ...
  },
  repair: function() {
    ...
  },
  getPrice: function() {
    return 399.00;
  }
};

/* The BicycleDecorator abstract decorator class. */

var BicycleDecorator = function(bicycle) { // implements Bicycle
  Interface.ensureImplements(bicycle, Bicycle);
  this.bicycle = bicycle;
}
BicycleDecorator.prototype = {
  assemble: function() {
    return this.bicycle.assemble();
  },
  wash: function() {
    return this.bicycle.wash();
  },
  ride: function() {
    return this.bicycle.ride();
  },
  repair: function() {
    return this.bicycle.repair();
  },
  getPrice: function() {
    return this.bicycle.getPrice();
  }
};

/* HeadlightDecorator class. */

var HeadlightDecorator = function(bicycle) { // implements Bicycle
  this.superclass.constructor(bicycle); // Call the superclass's constructor.
}
extend(HeadlightDecorator, BicycleDecorator); // Extend the superclass.
HeadlightDecorator.prototype.assemble = function() {
  return this.bicycle.assemble() + ' Attach headlight to handlebars.';
};
HeadlightDecorator.prototype.getPrice = function() {
  return this.bicycle.getPrice() + 15.00;
};


/* TaillightDecorator class. */

var TaillightDecorator = function(bicycle) { // implements Bicycle
  this.superclass.constructor(bicycle); // Call the superclass's constructor.
}
extend(TaillightDecorator, BicycleDecorator); // Extend the superclass.
TaillightDecorator.prototype.assemble = function() {
  return this.bicycle.assemble() + ' Attach taillight to the seat post.';
};
TaillightDecorator.prototype.getPrice = function() {
  return this.bicycle.getPrice() + 9.00;
};


/* Usage. */

var myBicycle = new AcmeComfortCruiser(); // Instantiate the bicycle.
alert(myBicycle.getPrice()); // Returns 399.00

myBicycle = new TaillightDecorator(myBicycle); // Decorate the bicycle object
                                               // with a taillight.
alert(myBicycle.getPrice()); // Now returns 408.00

myBicycle = new HeadlightDecorator(myBicycle); // Decorate the bicycle object
                                               // again, now with a headlight.
alert(myBicycle.getPrice()); // Now returns 423.00