JavaScript实现继承的三种方式：借用构造函数、拷贝继承与原型继承

function Person (name, age) {
  this.type = 'human'
  this.name = name
  this.age = age
}

function Student (name, age) {
  // 借用构造函数继承属性成员
  Person.call(this, name, age)
}

var s1 = Student('张三', 18)
console.log(s1.type, s1.name, s1.age) // => human 张三 18

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>title</title>
  <script>
    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) {
      //借用构造函数
      Person.call(this,name,age,sex,weight);
      this.score = score;
    }
    var stu1 = new Student("小明",10,"男","10kg","100");
    console.log(stu1.name, stu1.age, stu1.sex, stu1.weight, stu1.score);

    var stu2 = new Student("小红",20,"女","20kg","120");
    console.log(stu2.name, stu2.age, stu2.sex, stu2.weight, stu2.score);

    var stu3 = new Student("小丽",30,"妖","30kg","130");
    console.log(stu3.name, stu3.age, stu3.sex, stu3.weight, stu3.score);


  </script>
</head>
<body>


</body>
</html>

function Person (name, age) {
  this.type = 'human'
  this.name = name
  this.age = age
}

Person.prototype.sayName = function () {
  console.log('hello ' + this.name)
}

function Student (name, age) {
  Person.call(this, name, age)
}

// 原型对象拷贝继承原型对象成员
for(var key in Person.prototype) {
  Student.prototype[key] = Person.prototype[key]
}

var s1 = Student('张三', 18)

s1.sayName() // => hello 张三

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>title</title>
  <script>

    //拷贝继承；把一个对象中的属性或者方法直接复制到另一个对象中
    function Person() {
    }
    Person.prototype.age=10;
    Person.prototype.sex="男";
    Person.prototype.height=100;
    Person.prototype.play=function () {
      console.log("玩的好开心");
    };
    var obj2={};
    //Person的构造中有原型prototype,prototype就是一个对象,那么里面,age,sex,height,play都是该对象中的属性或者方法

    for(var key in Person.prototype){
      obj2[key]=Person.prototype[key];
    }
    console.dir(obj2);
    obj2.play();



  </script>
</head>
<body>


</body>
</html>

function Person (name, age) {
  this.type = 'human'
  this.name = name
  this.age = age
}

Person.prototype.sayName = function () {
  console.log('hello ' + this.name)
}

function Student (name, age) {
  Person.call(this, name, age)
}

// 利用原型的特性实现继承
Student.prototype = new Person()

var s1 = Student('张三', 18)

console.log(s1.type) // => human

s1.sayName() // => hello 张三

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>title</title>
  <script>


    //原型实现继承
    //借用构造函数实现继承
    //组合继承:原型继承+借用构造函数继承

    function Person(name,age,sex) {
      this.name=name;
      this.age=age;
      this.sex=sex;
    }
    Person.prototype.sayHi=function () {
      console.log("萨瓦迪卡");
    };
    function Student(name,age,sex,score) {
      //借用构造函数:属性值重复的问题
      Person.call(this,name,age,sex);
      this.score=score;
    }
    //改变原型指向----继承
    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();
    stu.eat();
    var stu2=new Student("小黑黑",200,"男人","1010分");
    console.log(stu2.name,stu2.age,stu2.sex,stu2.score);
    stu2.sayHi();
    stu2.eat();

    //属性和方法都被继承了
  </script>
</head>
<body>


</body>
</html>