25、class和继承

class Student{
  constructor(name,age){
    this.name = name;
    this.age = age;
  }
  sayHi(){
    console.log('hi'+this.name+this.age)
  }
}

let stu = new Student('smileyqp',100)

继承

• extends
• super
• 扩展或者重写方法

class Person(){
  constructor(name,age){
    this.name = name;
    this.age = age;
  }
  eat(){
    console.log(this.name+'eat food')
  }
}

class Student extends Person{
  constructor(name,age,number){
    super(name,age)
    this.number = number;
  }
  sayHi(){        //扩展方法
    console.log('hi'+this.name+this.age)
  }
}

class Teacher extends Person{
  constructor(name,age,major){
    super(name,age)
    this.major = major;
  }
  teach(){
    console.log(this.name+'teach'+this.major)
  }
}

let smileyqp = new Student('smileyqp',20)

//补充
smileyqp.eat()        //smileyqp eat food
smileyqp.__proto__.eat()        //会爆粗，因为它相当于在smileyqp.__proto__即Student的原型上去调用的，没有定义name所以会报错

instanceof

• instanceof可以去判断引用类型
• Object是所有class的父类

smileyqp instanceof Student;    //true
smileyqp instanceof Person;    //true
smileyqp instanceof Object;    //true

[] instanceof Array;    //true
{} instanceof Object;        //true
[] instanceof Object;        //true