参考《javascript设计模式》[美]Addy Osmani一书，下面介绍使用javascript经常会使用的主要设计模式。本博文是使用ES5语法的【下】篇，还有一个【上】篇，ES6语法会单独写个博客。
主要是以下几个设计模式：

Constructor Pattern 构造模式
Module Pattern 模块化模式
Revealing Module Pattern 揭露模块化模式
Singleton Pattern 单例模式
Observer Pattern 观察者模式
Mediator Pattern 中介者模式
Prototype Pattern 原型模式
Command Pattern 命令行模式
Facade Pattern 外观模式
Factory Pattern 工厂模式
Mixin Pattern 混入模式
Decorator Pattern 装饰者模式
Flyweight Pattern 享元模式

所有代码挂在我的github上，包含有ES5和ES6语法实现的内容。
https://github.com/zrysmt/javascript-design-pattern

6.Facade Pattern 外观模式

外观模式也是只暴露一个很简单的方法，然后该方法在内部执行，调用内部的其他方法，jquery使用了很多这种模式，如 $().css、$ .ajax()等

 var module = (function() {
     var _private = {
         i: 5,
         get: function() {
             console.log("current value:" + this.i);
         },
         set: function(val) {
             this.i = val;
         },
         run: function() {
             console.log("running");
         },
         jump: function() {
             console.log("jumping");
         }
     };
     return {
         facade: function(args) {
             _private.set(args.val);
             _private.get();
             if (args.run) {
                 _private.run();
             }
         }
     };
 }());
 // Outputs: "current value: 10" and "running"
 module.facade({ run: true, val: 10 });

7.Factory Pattern 工厂模式

怎么解释呢？工厂模式就是创建一个大型的制作工厂，然后其它的对象从这个工厂中产生。

//工厂
function VehicleFactory() {}
// Our default vehicleClass is Car 默认的是Car制造工厂
VehicleFactory.prototype.vehicleClass = Car;

VehicleFactory.prototype.createVehicle = function(options) {
    if (options.vehicleType === "car") {
        this.vehicleClass = Car;
    } else {
        this.vehicleClass = Truck;
    }
    return new this.vehicleClass(options);
};

两个具体的工厂里面的制作空间

function Car(options) {
    // some defaults
    this.doors = options.doors || 4;
    this.state = options.state || "brand new";
    this.color = options.color || "silver";
}
// A constructor for defining new trucks
function Truck(options) {
    this.state = options.state || "used";
    this.wheelSize = options.wheelSize || "large";
    this.color = options.color || "blue";
}

使用

var carFactory = new VehicleFactory();
var car = carFactory.createVehicle({
    vehicleType: "car",
    color: "yellow",
    doors: 6
});

console.log(car instanceof Car);// Outputs: true

8.Mixin Pattern 混入模式

简单解释下，混入就是将一个对象的方法复制给另外一个对象。

var Car = function(settings) {
    this.model = settings.model || "no model provided";
    this.color = settings.color || "no colour provided";
};

var Mixin = function() {};
Mixin.prototype = {
    driveForward: function() {
        console.log("drive forward");
    },
    driveBackward: function() {
        console.log("drive backward");
    },
    driveSideways: function() {
        console.log("drive sideways");
    }
};

function augment(receivingClass, givingClass) {
    if (arguments[2]) {
        for (var i = 2, len = arguments.length; i < len; i++) {
            receivingClass.prototype[arguments[i]] = givingClass.prototype[arguments[i]];
        }
    } else {
        for (var methodName in givingClass.prototype) {
            if (!Object.hasOwnProperty(receivingClass.prototype, methodName)) {
                receivingClass.prototype[methodName] = givingClass.prototype[methodName];
            }
        }
    }
}

// 只混入两个方法，Mixin的方法复制给Car
augment(Car, Mixin, "driveForward", "driveBackward");
// Create a new Car
var myCar = new Car({
    model: "Ford Escort",
    color: "blue"
});
myCar.driveForward();
myCar.driveBackward();

9.Decorator Pattern 装饰者模式

装饰模式是只针对一个基本的对象，添加一些修饰。如下面的是对MacBook，加内存（Memory函数装饰）增加75美元，雕刻（Engraving函数装饰）增加200美元，买保险（Insurance函数装饰）增加250美元。

function MacBook() {
    this.cost = function() {
        return 997; };
    this.screenSize = function() {
       return 11.6; };
}
// Decorator 1
function Memory(macbook) {
    var v = macbook.cost();
    macbook.cost = function() {
        return v + 75;
    };
}
// Decorator 2
function Engraving(macbook) {
    var v = macbook.cost();
    macbook.cost = function() {
        return v + 200;
    };
}
// Decorator 3
function Insurance(macbook) {
    var v = macbook.cost();
    macbook.cost = function() {
        return v + 250;
    };

}
var mb = new MacBook();
Memory(mb);
Engraving(mb);
Insurance(mb);

10.Flyweight Pattern 享元模式

享元模式我感觉就是共享一些数据或者方法，有一个工厂可以管理
* Flyweight
享元对象（类似于接口），提供的可以共享的属性/方法；
* Concrete Flyweight
具体享元对象，实现接口，具体实现享元对象的方法；
* Flyweight Factory
享元工厂对象，创建并管理flyweight对象

实现接口的方法，由于js没有，这里我们就模拟下。

//在js模拟存虚拟的继承，类似java中的implements
Function.prototype.implementsFor = function(parentClassOrObject) {
    if (parentClassOrObject.constructor === Function) {
        this.prototype = new parentClassOrObject();
        this.prototype.consturctor = this;
        this.prototype.parent = parentClassOrObject.prototype;
    }else {
        //纯虚拟继承
        this.prototype = parentClassOrObject;
        this.prototype.constructor = this;
        this.prototype.parent = parentClassOrObject;
    }
}

享元对象

// Flyweight object 享元对象
var CoffeeOrder = {
    // Interfaces 接口
    serveCoffee: function(context) {},
    getFlavor: function() {}
};

具体享元对象

// Implements CoffeeOrder
function CoffeeFlavor(newFlavor) {
    var flavor = newFlavor;
    if (typeof this.getFlavor === "function") {
        this.getFlavor = function() {
            return flavor;
        };
    }

    if (typeof this.serveCoffee === "function") {
        this.serveCoffee = function(context) {
            console.log("Serving Coffee flavor " + flavor + " to table number " + context.getTable());
        };
    }

}
// Implement interface for CoffeeOrder 实现接口
CoffeeFlavor.implementsFor(CoffeeOrder);

辅助器

function CoffeeOrderContext(tableNumber) {
    return {
        getTable: function() {
            return tableNumber;
        }
    };
}

享元工厂对象

//创建并管理flyweight对象
function CoffeeFlavorFactory() {
    var flavors = {},
        length = 0;

    return {
        getCoffeeFlavor: function(flavorName) {
            //这是个单例模式
            var flavor = flavors[flavorName];
            if (flavor === undefined) {
                flavor = new CoffeeFlavor(flavorName);//创建flyweight对象
                flavors[flavorName] = flavor;
                length++;
            }
            return flavor;
        },

        getTotalCoffeeFlavorsMade: function() {
            return length;
        }
    };
}

测试

testFlyweight()

function testFlyweight() {
    // The flavors ordered. 已订购的flavors
    var flavors = new CoffeeFlavor(),
        // The tables for the orders. 
        tables = new CoffeeOrderContext(),
        // Number of orders made 订单数量
        ordersMade = 0,
        // The CoffeeFlavorFactory instance
        flavorFactory;
    //flavorIn 订单物的名称
    function takeOrders(flavorIn, table) {
        flavors[ordersMade] = flavorFactory.getCoffeeFlavor(flavorIn);
        //flavorFactory管理者创建好后(管理者也做了处理)返回给CoffeeFlavor
        tables[ordersMade++] = new CoffeeOrderContext(table);
    }

    flavorFactory = new CoffeeFlavorFactory();

    takeOrders("Cappuccino", 2);
    takeOrders("Cappuccino", 2);
    takeOrders("Frappe", 1);
    takeOrders("Frappe", 1);
    takeOrders("Xpresso", 1);
    takeOrders("Frappe", 897);
    takeOrders("Cappuccino", 97);
    takeOrders("Cappuccino", 97);
    takeOrders("Frappe", 3);
    takeOrders("Xpresso", 3);
    takeOrders("Cappuccino", 3);
    takeOrders("Xpresso", 96);
    takeOrders("Frappe", 552);
    takeOrders("Cappuccino", 121);
    takeOrders("Xpresso", 121);

    for (var i = 0; i < ordersMade; ++i) {
        flavors[i].serveCoffee(tables[i]);
    }
    console.log(" ");
    console.log("total CoffeeFlavor objects made: " + flavorFactory.getTotalCoffeeFlavorsMade());
}