A brief analysis of JS prototype inheritance and class inheritance

A brief analysis of JS prototype inheritance and class inheritance_Basic knowledge

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Release： 2016-05-16 15:06:08

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Let’s look at the inheritance of JS classes first

<!DOCTYPE html>
<html>
 
<head>
  <meta charset="UTF-8">
    <title>JS类的继承</title>
</head>
 
<body>
  /* -- 类式继承 -- */
  <script type="text/javascript">
  //先声明一个超类
  var Animal = function(name) {
      this.name = name;
    }
    //给这个超类的原型对象上添加方法
  Animal.prototype.Eat = function() {
    console.log(this.name + " Eat");
  };
  //实例化这个超
  var a = new Animal("Animal");
 
  //再创建构造函数对象类
  var Cat = function(name, sex) {
      //这个类中要调用超类Animal的构造函数，并将参数name传给它
      Animal.call(this, name);
      this.sex = sex;
    }
    //这个子类的原型对象等于超类的实例
  Cat.prototype = new Animal();
  //因为子类的原型对象等于超类的实例，所以prototype.constructor这个方法也等于超类构造函数
 
  console.log(Cat.prototype.constructor);
  //这个是Animal超类的引用，所以要从新赋值为自己本身
  Cat.prototype.constructor = Cat;
  console.log(Cat.prototype.constructor);
  //子类本身添加了getSex 方法
  Cat.prototype.getSex = function() {
      return this.sex;
    }
    //实例化这个子类
  var _m = new Cat('cat', 'male');
  //自身的方法
  console.log(_m.getSex()); //male
  //继承超类的方法
  console.log(_m.Eat()); //cat
  </script>
</body>
 
</html>

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Let’s look at JS prototypal inheritance

<!DOCTYPE html>
<html>
 
<head>
  <meta charset="UTF-8">
  <title>JS原型继承</title>
</head>
 
<body>
  <!--原型继承-->
  <script type="text/javascript">
  //clone()函数用来创建新的类Person对象
  var clone = function(obj) {
    var _f = function() {};
    //这句是原型式继承最核心的地方，函数的原型对象为对象字面量
    _f.prototype = obj;
    return new _f;
  }
 
  //先声明一个对象字面量
  var Animal = {
      somthing: 'apple',
      eat: function() {
        console.log("eat " + this.somthing);
      }
    }
    //不需要定义一个Person的子类，只要执行一次克隆即可
  var Cat = clone(Animal);
  //可以直接获得Person提供的默认值，也可以添加或者修改属性和方法
  console.log(Cat.eat());
  Cat.somthing = 'orange';
  console.log(Cat.eat());
 
  //声明子类,执行一次克隆即可
  var Someone = clone(Cat);
  </script>
</body>
 
</html>

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We can try it out. JS class inheritance children.constructor==father returns true, while prototypal inheritance children.constructor==father returns false;

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