一、html代码
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>JS实现倒计时(时、分，秒)</title>
</head>
<body>
<div id="divdown1"></div>
<script language="javascript" type="text/javascript">
var interval = 1000;
function ShowCountDown(year, month, day, divname) {
var now = new Date();
var endDate = new Date(year, month - 1, day);
var leftTime = endDate.getTime() - now.getTime();
var leftsecond = parseInt(leftTime / 1000);
//var day1=parseInt(leftsecond/(24*60*60*6));
var day1 = Math.floor(leftsecond / (60 * 60 * 24));
var hour = Math.floor((leftsecond - day1 * 24 * 60 * 60) / 3600);
var minute = Math.floor((leftsecond - day1 * 24 * 60 * 60 - hour * 3600) / 60);
var second = Math.floor(leftsecond - day1 * 24 * 60 * 60 - hour * 3600 - minute * 60);
var cc = document.getElementById(divname);
cc.innerHTML = "小胡同志提示距离" + year + "年" + month + "月" + day + "日还有：" + day1 + "天" + hour + "小时" + minute + "分" + second + "秒";
}
window.setInterval(function() {
ShowCountDown(2020, 12, 31, 'divdown1');
}, interval);
</script>
</body>
</html>