//寄生组合式继承就是为了降低调用父类构造函数的开销而出现的
//基本思路是: 不必为了指定子类型的原型而调用超类型的构造函数
function extend(subClass,superClass){
var F = function(){};
F.prototype = superClass.prototype;
//subClass.prototype =superClass.prtotype相当于原型共享而非继承
subClass.prototype = new F();//继承superClass的原型
subClass.prototype.constructor = subClass;//原型重写，手动绑定
subClass.superclass = superClass.prototype;//将superClass.prototype缓存起来，方便后续访问
if(superClass.prototype.constructor == Object.prototype.constructor){
superClass.prototype.constructor = superClass;
}
}
function Father(name){
this.name = name;
this.colors = ["red","pink","green"];
}
Father.prototype.sayname = function(){
console.log(this.name);
}
function Son(name,age){
Father.call(this,name);//使用构造函数进行实例属性的继承，调用第一次
this.age = age;
}
extend(Son,Father);//
Son.prototype.constructor = Son;//重新指向Son
Son.prototype.sayage = function(){
console.log(this.age);
}
var instance1 = new Son("lisi",12);
instance1.colors.push("brown");
console.log(instance1.colors);
instance1.sayname();
instance1.sayage();
var instance2 = new Son("hah",22);
instance2.colors.push("black");
console.log(instance2.colors);
instance2.sayname();
instance2.sayage();
