2-7 class

1-1 class定义一个简单的类

class Person{
            constructor(name,age){
                this.name = name;
                this.age = age
            }
}

直接定义在class中的属性,还是实例私有的属性。

class Person{
            skill = "javascript"
            constructor(name,age){
                this.name = name;
                this.age = age
            }
}

 console.log(p.hasOwnProperty("skill"))

1-2 共有方法

class Person {
            constructor(name, age) {
                this.name = name;
                this.age = age
            }
            sayName(){
                console.log(this.name)
            }
}
 var p = new Person("cheng", 18);
p.sayName()

1-3 添加共有的方法

Object.assign()

es6不支持使用直接量的方式在原型上添加

     class Person {
            constructor(name, age) {
                this.name = name;
                this.age = age
            }
            sayName() {
                console.log(this.name)
            }
        }
        Person.prototype = {
            sayAge() {
                console.log(this.age)
            }
        } 
# 会报错

            class Person {
            constructor(name, age) {
                this.name = name;
                this.age = age
            }
            sayName() {
                console.log(this.name)
            }
        }
        Object.assign(Person.prototype,{
            sayAge(){
                console.log(this.name)
            },
            saySkill(){
                console.log("前端")
            }
        })
        var p = new Person("cheng",16);
        p.sayAge()

1-4 继承

class Person{
  constructor(name,age){
    this.name = name;
    this.age = age
  }
  sayName(){
    console.log(this.name);
  }
}
class Teacher extends Person{
  // 类继承之后，构造函数第一行必须写super关键字，去继承父类的属性
  constructor(name,age,skill){
    super(name,age)
    this.skill = skill 
  }
  // 在子类的方法中调用父类的方法 (this或super去调用)
  show(){
    super.sayName()
    // this.sayName()
  }
}
var t = new Teacher("zhang",18,"js")
console.log(t);
t.sayName()