this指向

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this指向的讲解

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

function Test(b){
    this.d=3;
    var a=1;
    function c(){
    }
}
Test(123)
console.log(window.d)
//

运行结果

案例2

function Test(){
    this.name='123'
}
var test=new Test()
console.log(test.name)




function Person(name,age){
    this.name="geyao"
    this.age=18
}
function Programmer(name,age){
    Person.apply(this,[name,age])
    this.work="Programmer"
}
var p=new Programmer("geyao",18)
console.log(p)

运行结果