怎么用JS写一个倒计时

一小时倒计时，代码如下：<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>js实现倒计时思路</title> <style type="text/css"> *{ margin:0; padding:0; font-size:50px; } #wrap{ width:300px; height:200px; border:1px solid #abcdef; position:absolute; left:50%; top:50%; transform:translate(-50%,-50%); text-align:center; line-height:200px; } </style> <script type="text/javascript"> window.onload = function(){ var hour = document.getElementById('hour'); var minute = document.getElementById('minute'); var second = document.getElementById('second'); var hourNum = 0; var minuteNum = 59; var secondNum = 60; var timer = window.setInterval(function(){ if(secondNum!=0){ secondNum--; if(secondNum<10){ secondNum = '0'+secondNum; } }else{ secondNum = 59; //秒数为零时，时间走了一分钟，分钟数要减一 minuteNum--; if(minuteNum<10&&minuteNum>0){ minuteNum = '0'+minuteNum; } } if(minuteNum == 0){ //分钟数为零时，时间走了一小时，停止定时器 secondNum = '00'; minuteNum = '00'; window.clearInterval(timer); } hour.innerHTML = hourNum; minute.innerHTML = minuteNum; second.innerHTML = secondNum; },1000); } </script> </head> <body> <div id="wrap"> <span id="hour">1</span>:<span id="minute">00</span>:<span id="second">00</span> </div> </body> </html>

怎么用JS写一个倒计时

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