ES6 extends继承

原理:

ES6的class继承关键子、核心也是利用了寄生式组合继承的方式

代码理解

class User{
  constructor(name){
    this.name = name;
  }
  getName(){
    console.log(this.name)
  }
}
class CreateUser extends User{
  constructor(name, age){
    super(name)
    this.age = age
  }
  getAge(){
    console.log(this.age)
  }
}
let users = new CreateUser('gf', 18);
users.getName() // gf

extends实现原理

function _extends(subType, superType){
   subType.prototype = Object.create(superType && superType.prototype, {
      constructor: {
        value: subType,
        enumerable: false,
        writable: true,
        configurable: true
      }
    });
    if(subType){
      Object.setPrototypeOf 
        ? Object.setPrototypeOf(subType, superType)
        : subType.__proto__ = superType;
    }
}
function User(name) {
    this.name = name;
}
User.prototype.getName = function () { console.log(this.name) };
function CreateUser(name, age) {
    this.age = age;
    User.call(this, name);
    Hobby.call(this);
}
_extends(CreateUser, User);
let users = new Create('lisi',18)
// 这里有问题,今天先这样吧、明天研究这个