JavaScript模式读书笔记 第7章 设计模式

<script>
	//obj为单例
	var obj = {
		
		myProp: "My Value"
	};
	var obj1 = obj;
	var obj2 = obj;
	console.log(obj1 == obj2);//true
	console.log(obj1 === obj2);//true
  </script>

 <script>
	function Universe(){
		
		if(typeof Universe.instance === "object"){
			
			return Universe.instance;
		}
 
		this.start_time = 0;
		this.bang = "Big";
 
		Universe.instance = this;
	}
 
	var u1 = new Universe();
	var u2 = new Universe();
	console.log(u1 === u2);//true
  </script>

  <script>
	 function Universe(){
		//缓存私有变量
		var instance = this;
 
		this.start_time = 0;
		this.bang = "Big";
		
		//重写构造函数，返回私有变量
		Universe = function(){
			
			return instance;
		};
	 }
	 var u1 = new Universe();
	 var u2 = new Universe();
	 console.log(u1 === u2);//true
  </script>

 function Universe(){
		//缓存私有变量
		var instance ;
 
		
		
		//重写构造函数，返回私有变量
		Universe = function  Universe(){
			
			return instance;
		};
		//保留原属性
		Universe.prototype = this;
		//创建实例 
		instance = new Universe();
		//重置构造函数指针
		instance.constructor = Universe;
 
 
		this.start_time = 0;
		this.bang = "Big";
 
		return instance;
	 }
	
	 Universe.prototype.nothing = true;
	 var u1 = new Universe();
	
		
	 Universe.prototype.everything = true;
     var u2 = new Universe();
 
	 
	 console.log(u1.nothing);//true
	 console.log(u2.nothing);//true
     console.log(u1.everything);//true
	 console.log(u2.everything);//true
  </script>

<script>
	var o = new Object(),
		n = new Object(1),
		s = Object(‘1‘),
		b = Object(true);
 
	
	console.log(o.constructor === Object);//true
	console.log(n.constructor === Number);//true
	console.log(s.constructor === String);//true
	console.log(b.constructor === Boolean);//true
  </script>

  <script>
	var sale = new Sale(100);
	sale = sale.decorator("fedtax");//增加联邦税
	sale = sale.decorator("quebec");//增加省税
	sale = sale.decorator("money");//以美元形式展示
	sale.getPrice();//"$112.88"
 
	//使用不同的税收策略
	var sale = new Sale(100);
	sale = sale.decorator("fedtax");//增加联邦税
	sale = sale.decorator("cdn");//以cdn形式展示
	sale.getPrice();//"CDN$ 105.88"
  </script>

<script>
	
	function Sale(price){
		
		this.price = price || 100;
	}
	
	Sale.prototype.getPrice = function(){
		
		return this.price;
	};
	//装饰者对象
	Sale.decorators = {};
 
	//装饰者从父对象获取值，然后再修改该值
	Sale.decorators.fedtax = {
		
		getPrice: function(){
			
			var price = this.uber.getPrice();
			price += price * 0.005;
			return price;
		}
	};
	Sale.decorators.quebec = {
		
		getPrice: function(){
			
			var price = this.uber.getPrice();
			price += price * 0.075;
			return price;
		}
	};
	Sale.decorators.money = {
		
		getPrice: function(){
			
			return "$" + this.uber.getPrice().toFixed(2);
		}
	};
	Sale.decorators.cdn = {
		
		
		getPrice: function(){
			
			return "CDN$" + this.uber.getPrice().toFixed(2);
		}
	};
 
	Sale.prototype.decorator = 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.decorator("fedtax");//增加联邦税
	sale = sale.decorator("quebec");//增加省税
	sale = sale.decorator("money");//以美元形式展示
	console.log(sale.getPrice());//"$112.88"
 
	//使用不同的税收策略
	var sale = new Sale(100);
	sale = sale.decorator("fedtax");//增加联邦税
	sale = sale.decorator("cdn");//以cdn形式展示
	console.log(sale.getPrice());//"CDN$ 105.88"
  </script>