13 定时器
1 setInterval
2 setTimeout
3 关掉定时器
1 setInterval
定时任务 每隔3s执行一次DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Titletitle>
<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.4.1/jquery.min.js">script>
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.4.1/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.4.1/js/bootstrap.min.js">script>
head>
<body>
<script>
let t = setInterval(function () {
console.log(111)
},3000)
script>
body>
html>
每隔3秒执行一次
2 setTimeout
延迟任务，只执行一次
DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Titletitle>
<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.4.1/jquery.min.js">script>
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.4.1/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.4.1/js/bootstrap.min.js">script>
head>
<body>
<script>
let t = setTimeout(function () {
console.log(111)
},3000)
script>
body>
html>
3 关掉定时器
clearInterval(this.t)