面向对象----继承

三、 组合继承 （原型链和借用构造函数的技术组合到一起） 

```javascript
function SuperType(name){
this.name = name;
this.colors = ['red','yellow'];
}

SuperType.prototype.sayName = function(){
alert(this.name)
}

function SubType(name,age){
// 继承属性 
SuperType.call(this,name);
this.age = age;
}

//继承方法
SubType.prototype = new SuperType();
SubType.prototype.constructor = SubType;
SubType.prototype.sayAge = function(){
alert(this.age);
}

var a = new SubType("Alex",18);
var b = new SubType("John",21);
a.colors.push("black");
console.log(a.colors)//['red','yellow','black'];
a.sayName();//Alex
a.sayAge();//18

b.colors;//["red","yellow"];

　　四、寄生组合式继承（集寄生式继承和组合继承的优点于一身，是实现基于类型继承的最有效方式）

function SuperType(name){
		  	 this.name = name;
		  }
		  
		  SuperType.prototype.sayName = function(){
		  	   alert(this.name);
		  }
		  
		  function SubType(name,age){
		  	   SuperType.call(this,name);
		  	   this.age = age;
		  }
		  
		  function object(o){
		  	 function F(){};
		  	 F.prototype = o;
		  	 return new F();
		  }
		  
		  function inheritProtyotype(sub,parent){
		  	  var prototype = object(parent.prototype);
		  	  prototype.constructor = sub;
		  	  sun.prototype = prototype;
		  }