JS学习笔记之原型链和利用原型实现继承详解

 function Animal(name,age){
    this.name=name;
    thia.age=age;
   }

   //在原型中添加方法
   Animal.prototype.eat=function(){
    console.log("动物吃草")
    this.play()
   }
   Animal.prototype.play=function(){
    console.log("玩啥呢")
   }

 function Student(name,age,sex){
      this.name=name;
      this.age=age;
      this.sex=sex;
   }
  
   Student.prototype.height="188"
   Student.prototype.weight="55kg"
   Student.prototype.study=function(){
      console.log("好好学习i")
    }
  var stu=new Student("小红",20,"男")
  console.dir(stu)

 function Student(name,age,sex){
      this.name=name;
      this.age=age;
      this.sex=sex;
   }
  Student.prototype={
    height:"188",
    weight:"55kg",
    study:function(){
      console.log("好好学习i")
    }
   }
  var stu=new Student("小红",20,"男")
  console.dir(stu)

function Student(name,age,sex){
      this.name=name;
      this.age=age;
      this.sex=sex;
   }
  Student.prototype={
    constructor:Student,
    height:"188",
    weight:"55kg",
    study:function(){
      console.log("好好学习i")
    }
   }
  var stu=new Student("小红",20,"男")
  console.dir(stu)

Student.prototype=new Person(10);

function Person(name,age,sex,weight){
  this.name=name;
  this.age=age;
  this.sex=sex;
  this.weight=weight;
}
Person.prototype.sayHi=function(){
  console.log("您好")
}

function Student(name,age,sex,weight,score){
  //将当前实例对象传入Person 借过来使用一次来达到继承效果
  Person.call(this,name,age,sex,weight);
  this.score=score;
}

var stu1=new Student("小明",10,"男","10kg","100")

Student.prototype.constructor=Student

function Person(name,age){
    this.name=name;
    this.age=age;
   }

   Person.prototype.eat=function(){
    console.log("Person 吃饭")
   }

   function Student(num,score){
    this.num=num
    this.score=score
   }
   //继承
  Student.prototype=new Person("小红",10)
  Student.prototype.constructor=Student

  var stu =new Student(2016002288,80)

  stu.eat()//Person 吃饭

function Person(name,age,sex){
    this.name=name;
    this.age=age;
    this.sex=sex;
   }
   Person.prototype.sayHi=function(){
    console.log("你好")
   }

   function Student(name,age,sex,score){
    //借用构造函数
    Person.call(this,name,age,sex)
    this.score=score
   }

   // 改变了原型指向
   Student.prototype=new Person();//不传值
   Student.prototype.eat=function(){
    console.log("吃东西");
   }

   var stu=new Student("小黑",20,"男","100分")
   console.log(stu.name,stu.age,stu.sex,stu.score);
   stu.sayHi()//你好
   stu.eat()//吃东西

function Person(){
  }

  Person.prototype.name="小红"
  Person.prototype.age=18

  function Student(){
  }
  
  var p=Person.prototype;
  var s=Student.prototype;

  for(key in p){
    s[key]=p[key]
  }

  console.dir(Student)

function extend(Child,Parent) {

　　　　var p = Parent.prototype;
　　　　var c = Child.prototype;

　　　　for (var i in p) {
　　　　　　c[i] = p[i];
　　　　　　}
    
    //这个属性直接指向父对象的prototype属性,可以直接调用父对象的方法,为了实现继承的完备性，纯属备用性质
　　　　c.par = p;

　　}

  function Person(){};

  Person.prototype.name="小红";
  Person.prototype.age=18;

  function Student(){};

  Student.prototype=Person.prototype;

  console.dir(Student);
  console.dir(Person);
  Student.prototype.age=25;

function Person(){};
  Person.prototype.name="小红";
  Person.prototype.age=11;

  function Student(){};
  var F=function(){};
  F.prototype=Person.prototype;

  Student.prototype=new F();
  Student.prototype.constructor=Student;

  Student.prototype.age=25;

  console.dir(Person)
  console.dir(Student)

function extend(Child,Parent) {

　　　　var F = function(){};

　　　　F.prototype = Parent.prototype;

　　　　Child.prototype = new F();

　　　　Child.prototype.constructor = Child;

　　　　Child.par = Parent.prototype;

　　}