day41 -内部对象和继承

内部对象

data日期内置函数

var now = new Date();
 console.log(now);//打印当前时间
 now.getFullYear()//年
 now.getMonth()//月
 now.getDate()//日
 now.getDay()//星期几
 now.getTime()//时间戳
 now.toLocaleString()//转换为字符串

JSON

JSON轻量级的数据交换格式，提升网络传输效率

 var user ={
     name:'gugu',
     age:22,
     sex:'boy'
 }

转化为json字符串

//对象转化为json字符串
 var jsonuser = JSON.stringify(user)
 // console.log(user)
 // 1 {name: 'gugu', age: 22, sex: 'boy'}age: 22name: "gugu"sex: "boy"[[Prototype]]: Object
 
 // console.log(jsonuser)
 // 1 {"name":"gugu","age":22,"sex":"boy"}

json字符串转化为对象，参数为字符串

 var user1=JSON.parse('{"name":"gugu","age":22,"sex":"boy"}')
 
 // console.log(user1)
 // {name: 'gugu', age: 22, sex: 'boy'}age: 22name: "gugu"sex: "boy"[[Prototype]]: Object

面向对象编程

最初的继承方法：proto

var user ={
     name:'gugu',
     age:22,
     sex:'boy',
     run: function (){
         console.log(this.name+'run ...')
     }
 }
 var gu ={
     name:'gu'
 };
 gu.__proto__=user;//最初的原型继承方法

class继承

 //定义一个学生类
 class student{
 
     constructor(name) {
         this.name = name;
     }
     hello(){
         alert('hello')
     }
 }
 var gugu=new student('gugu')
 gugu.hello();
 gugu.name
 var xixi=new student('xixi')

继承学生类

 //继承
 class xiaostudent extends student{
     constructor(name,grade) {
         super(name);
         this.grade = grade;
     }
     mygrade(){
         console.log('mygrade '+this.grade)
     }
 }
 var hha=new xiaostudent('hah',99)