如何用JavaScript写出一个计时器
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script type="text/javascript">
/**
* 常用方法
*/
var today=new Date();
var year=today.getFullYear();
var month=today.getMonth()+1;
var date=today.getDate();
var hour=today.getHours();
var minute=today.getMinutes();
var second=today.getSeconds();
var milliSecond=today.getMilliseconds();
var day=today.getDay();
var weekday=['星期日','星期一','星期二','星期三','星期四','星期五','星期六'];
var time=today.getTime(); // 返回从1970-01-01 00:00:00至今的毫秒数
console.log(year+'年'+month+'月'+date+'日 '+hour+':'+minute+':'+second+' '+milliSecond+' '+weekday[day]);
function showTime(){
var today=new Date();
var duoHand=new Date(2021,5,18);//时间
var seconds=Math.floor((duoHand.getTime()-today.getTime())/1000);
if(seconds<=0){
document.getElementById('time').innerHTML='可以开始剁手了！';
return;
}
var day=Math.floor(seconds/60/60/24);
var hour=checkNum(Math.floor(seconds/60/60%24));
var minute=checkNum(Math.floor(seconds/60%60));
var second=checkNum(seconds%60);
var time='距离6·18还有：'+day+'天 '+hour+'小时'+minute+'分'+second+'秒';//判断时间
document.getElementById('time').innerHTML=time;
setTimeout(showTime,1000);
}
function checkNum(num){
if(num<10){
return '0'+num;
}
return num;
}
window.onload=function(){
showTime();
}
</script>
</head>
<body>
<div id="time"></div>
</body>
</html>