前端歌谣-第十捌课-对象属性的遍历

前言

我是歌谣 最好的种树是十年前 其次是现在 今天继续给大家带来的是对象属性的讲解

环境配置

npm init -y
yarn add vite -D

修改page.json配置端口

{
  "name": "demo1",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "dev": "vite --port 3002"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "vite": "^4.4.9"
  }
}

案例1

var arr=[1,2,3,4,5]
for(var i=0;i<arr.length;i++){
    console.log(arr[i])
}

运行结果

案例2

 var arr=[1,2,3,4,5]
// for(var i=0;i<arr.length;i++){
//     console.log(arr[i])
// }
var car={
    brand:'Benz',
    color:'red',
    displament:'3.0',
    name:'geyao'
}
for(var key in car){
    console.log(key+'+'+car[key])
}
for(var key in arr){
    console.log(arr[key])
}

运行结果

案例3

var obj={
    name:"geyao",
    age:22
}
function Car(){
    this.brand="Benz",
    this.color="red",
    this.size=18
}
Car.prototype={
    age:18,
    width:2.5
}
Object.prototype.sex="女"
var car=new Car()
for(var key in car){
    console.log(key+'+'+car[key])
}

运行结果

案例4

var geyao={
    name:"geyao",
    age:18
}
console.log('age' in geyao) //true
 
function Car(){
    this.brand='TAGE',
    this.color='red'
}
Car.prototype={
    displacement:'3.0'
}
var car=new Car();
console.log('displacement' in car)

运行结果

案例5

function Car(){
 
}
var car=new Car()
 
function Person(){
 
}
console.log(car instanceof Car)
console.log(car instanceof Object)
console.log([] instanceof Array)
console.log([] instanceof Object)
console.log({} instanceof Object)

运行结果

案例6

const a=[]
console.log(a.constructor)
console.log( a instanceof Array)
var str=Object.prototype.toString.call(a)
console.log(str)
 
var arr=new Array(1,2,3)
console.log(arr)

运行结果