继承
1.传统形式 ——> 原型链
　　过多的继承了没用的属性
2.借用构造函数
　　1.不能继承借用构造函数的原型
　　2.每次构造函数都要多走一个函数
3.共享原型
　　不能随便改动自己的原型
4.圣杯模式

1.传统形式 ——> 原型链

Grand.prototype.lastName = "Ji"
function Grand(){

}
var grand = new Grand();
Father.prototype = grand;
function Father(){
    this.name = 'hehe'
}
var father = new Father();
Son.prototype = Father;
function Son(){

}
var son = new Son();

2.借用构造函数

function Person(name,age,sex){
    this.name = name;
    this.age = age;
    this.sex = sex;
}
function Student(name,age,sex,grade){
    Person.call(this,name,age,sex);
    this.grade = grade;
}
var student = new Student();

3.共享原型

Father.prototype.lastName = "Deng"
function Father(){

}
function Son(){

}
son.prototype = Father.prototype;
var son = new Son();
var father = new Father();
son.lastName    //"Deng"
Father.lastName //"Deng"

//封装继承
function inherit(Target,Origin){
    Target.prototype = Origin.prototype;
}
inherit(Son,father);
Son.prototype.sex = "male"
var son = new Son();
var father = new Father();

son.sex        //male
father.sex  //male

4.圣杯模式

//思路
function F(){}
F.prototype = Father.prototype;
Son.prototype = new F();

Father.prototype.lastName = "Deng"
function Father(){

}
function Son(){

}
function inherit(Target,Origin){
    function F(){}
    F.prototype = Origin.prototype;
    Target.prototype = new F();
    Target.prototype.constuctor = Target;      //修正constructor
    Target.prototype.uber = Origin.prototype; //找真正继承自谁
}
inherit(Son,father);
Son.prototype.sex = "male"

var son = new Son();
var father = new Father();

son.lastName //Deng
son.sex         //male
father.sex   //undefined

// son.__proto__ --> new F().__proto__ --> Father.prototype

//改写
var inherit = (function(){
    var F = function(){};//私有化变量
    return function (Target,Origin){
        F.prototype = Origin.prototype;
        Target.prototype = new F();
        Target.prototype.constuctor = Target;     
        Target.prototype.uber = Origin.prototype; 
    }
}());

//闭包，封装实现变量私有化
function Deng(name,wife){
    var prepareWife = "xiaozhang";//只有下面的方法能访问，外面Deng.prepareWife访问不了
    this.name = name;
    this.wife = wife;
    this.divorce = function(){
        this.wife = prepareWife;
    }
    this.changePrepareWife = function(target){
        prepareWife = target;
    }
    this.sayPraprewife = function (){
        console.log(prepareWife)
    }
}
var deng = new Deng('deng','xiaoliu');