单体模式：保证一个特定类仅有一个实例;即第二次使用同一个类创建新对象时，应该得到与第一个所创建对象完全相同对象；
- 在JS中，可以认为每次在使用对象字面量创建对象的时候，实际上就在创建一个单体；
- 当使用new创建新对象时
- 使用静态属性中的实例：
function Universe() {
if(typeof Universe.instance === 'object') {
return Universe.instance;
}
this.start_time = 0;
this.bang = 'Big';
Universe.instance = this;
return this;
} - 采用闭包包含单个实例：
function Universe1() {
var instance = this;
this.start_time = 0;
this.bang = 'Big';
Universe1 = function() {
return instance;
}
}var Universe;
(function () {
var instance;
Universe = function Universe() {
if(instance) {
return instance;
}
instance = this;
//增加功能
this.start_time = 0;
this.bang = 'Big';
}
})();
- 使用静态属性中的实例：
工厂模式：
根据字符串指定地类型在运行时创建对象地方法
工厂模式地目的使为了创建对象
- 当创建对象时执行重复操作
- 再编译时不知道具体类型地情况下，为工厂客户提供一个创建对象的接口
function CarMaker() {};
CarMaker.prototype.drive = function() {
return "Vroom, I have " + this.doors + " doors";
};
CarMaker.factory = function(type) {
var constr = type, newcar;
//如果构造函数不存在，则抛出错误
if(typeof CarMaker[constr] != "function") {
throw {
name: "Error",
message: constr + " doesn't exist"
};
}
//构造函数是已知存在的；使原型继承父类，但仅继承一次
if(typeof CarMaker[constr].prototype.drive !== 'function') {
CarMaker[constr].prototype = new CarMaker();
}
//创建一个新的实例
newcar = new CarMaker[constr]();
//选择性地调用一些方法，然后返回
return newcar;
};
CarMaker.Compact = function() {
this.doors = 4;
};
CarMaker.Convertible = function() {
this.doors = 2;
}
CarMaker.SUV = function() {
this.doors = 24;
}
var corolla = CarMaker.factory('Compact');
var solstice = CarMaker.factory('Convertible');
var cherokee = CarMaker.factory('SUV');
corolla.drive()；
solstice.drive()；
cherokee.drive()；
内置对象工厂：对于自然工厂的例子，可以考虑内置的Object()构造函数；它也根据输入类型而创建不同的对象；
迭代器模式：
提供一个API来遍历或操纵复杂地自定义数据结构
迭代访问一个包含某些数据集合的对象的模式；
var agg = (function() {
var index = 0, data = [1,2,3,4,5], length = data.length;
return {
next: function() {
var element;
if(!this.hasNext()) {
return null;
}
element = data[index];
index = index + 2;
return element;
},
hasNext: function() {
return index < length;
},
//重置指针到初始化位置
rewind: function() {
index = 0;
},
//返回当前元素
current: function() {
return data[index];
}
}
}());
//测试
while(agg.hasNext()) {
console.log(agg.next());
}
agg.rewind();
console.log(agg.current());
装饰者模式
可以再运行时动态添加附加功能到对象中；比较方便的特征时其预期行为可制定和可配置；
function Sale(price) {
this.price = price || 100;
}
Sale.prototype.getPrice = function() {
return this.price;
}
Sale.decorators = {};
//增加联邦税
Sale.decorators.fedtax = {
getPrice: function() {
var price = this.uber.getPrice();
price += price * 5/ 100;
return price;
}
};
//增加省级税
Sale.decorators.quebec = {
getPrice: function() {
var price = this.uber.getPrice();
price += price * 7.5 /100;
return price;
}
};
//转化为美元
Sale.decorators.money = {
getPrice: function() {
return "$" + this.uber.getPrice().toFixed(2);
}
};
//格式化为CDN
Sale.decorators.cdn = {
getPrice: function() {
return "CDN$ " + this.uber.getPrice().toFixed(2);
}
};
Sale.prototype.decorate = function(decorator) {
var F = function() {},
overrides = this.constructor.decorators[decorator],
i, newobj;
F.prototype = this;
newobj = new F();
newobj.uber = F.prototype;
for(i in overrides) {
if(overrides.hasOwnProperty(i)) {
newobj[i] = overrides[i];
}
}
return newobj;
}
var sale = new Sale(100);
sale = sale.decorate('fedtax');
sale = sale.decorate('quebec');
sale = sale.decorate('money');
sale.getPrice();
var newsale = new Sale(200);
newsale = newsale.decorate('cdn');
newsale.getPrice();
使用列表实现
function Sale(price) {
this.price = price;
this.decorators_list = [];
}
Sale.decorators = {};
Sale.decorators.fedtax = {
getPrice: function(price) {
return price + price * 5 / 100;
}
};
Sale.decorators.quebec = {
getPrice: function(price) {
return price + price * 7.5 /100;
}
};
Sale.decorators.money = {
getPrice: function(price) {
return "$" + price.toFixed(2);
}
};
Sale.prototype.decorate = function(decorator) {
this.decorators_list.push(decorator)
};
Sale.prototype.getPrice = function() {
var price = this.price, i, max = this.decorators_list.length, name;
for(i = 0; i < max; i++) {
name = this.decorators_list[i];
price = Sale.decorators[name].getPrice(price);
}
return price;
}
var sale = new Sale(100);
sale.decorate('fedtax');
sale.decorate('quebec');
sale.decorate('money');
console.log(sale.getPrice());