Detailed explanation of multiple inheritance examples in JavaScript

This article mainly introduces the method of implementing multiple inheritance in JavaScript. It analyzes the specific steps and related operating techniques of implementing multiple inheritance in JavaScript in detail with examples. Friends who need it can refer to it. I hope it can help everyone.

1. Define an empty parent class constructor, and then define properties and methods for the parent class through prototype

2. Define an empty subclass constructor, and then define The prototype of the subclass is bound to the instance of the parent class, and then the parent class of the prototype of the subclass is also bound to the instance of the parent class. Set your own properties and methods for subclasses through prototype.

3. Define an empty grandson class constructor, then bind the grandson class prototype to the subclass instance, and then bind the parent class of the grandson class prototype to the subclass instance. Define your own properties and methods for the grandchild class through prototype.

4. Instantiate a grandchild object. By calling the instance object, you can call its own method. You can also call the method of the grandchild's parent class, that is, the subclass in this article, or you can directly call the largest parent class, that is, The methods of the parent class here can also add properties and methods to the current object.

function Person(){}
Person.prototype.name = "人";// 为人类创建一个name属性
Person.prototype.say = function(content){// 为人类创建一个说话的方法
  if(!this.name){ // 如果对象不存在name属性，则使用原型链的name
    this.name = this.__proto__.name;
  }
  console.log("我是" + this.name + ",我想说"+content);
};
function Parent(){}
Parent.prototype = new Person();  // 设置Parent类继承Person类
Parent.prototype.superClass = new Person();// 设置superClass保存父类Person的方法属性
Parent.prototype.name = "父辈类";// 设置Parent类的name属性
Parent.prototype.say = function(){// 设置Parent类自己的 say 方法
  console.log("我是Parent类的say方法！");
};
function Child(){}
Child.prototype = new Parent();// 设置Child类继承Parent类
Child.prototype.superClass = new Parent();// 设置superClass保存父类Parent的方法属性
Child.prototype.say = function(){  //设置Child类自己的say方法
  console.log("我是Child类的say方法！");
}
var c = new Child();// 实例化一个Child对象
c.say();  // 调用自身原型的say方法，输出：我是Child类的say方法！
c.superClass.say(); // 调用父类Parent的say方法，输出： 我是Parent类的say方法！
c.superClass.superClass.say("哈哈");// 直接调用最大的父类Person的say方法(方法中的this指向Person)，输出：我是人,我想说哈哈"
// 用call调用最大的父类Person的say方法(方法中的this指向实例化对象c，但此时c并没有name属性，所以this.name用的是Parent的name)
c.superClass.superClass.say.call(c,"嘻嘻"); // 输出：我是父辈类,我想说嘻嘻
c.name = "子类实例";// 给当前对象增加name属性
// 还是用call调用最大父类Person的say方法(此时c对象中已经有name属性);
c.superClass.superClass.say.call(c,"我是子类的实例化对象"); // 输出：我是子类实例,我想说我是子类的实例化对象

ps:Multiple inheritance can add a new attribute on the prototype object to save the object and attributes of the parent class, when called by the subclass Use superClass to point out the parent class method. This solves the problem that the parent class and the subclass method have the same name, and the subclass will overwrite the parent class method after inheriting the parent class.

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