效果：
javascript：
???<script type="text/javascript"> ???????function countTime() { ???????????//获取当前时间 ???????????var date = new Date(); ???????????var now = date.getTime(); ???????????//设置截止时间 ???????????var endDate = new Date("2018-10-25 00:00:00"); ???????????var end = endDate.getTime(); ???????????//时间差 ???????????var differTime = end - now; ???????????//定义变量,h,m,s保存倒计时的时间 ???????????var h, m, s; ???????????if (differTime >= 0) { ???????????????h = Math.floor(differTime / 1000 / 60 / 60); ???????????????m = Math.floor(differTime / 1000 / 60 % 60); ???????????????s = Math.floor(differTime / 1000 % 60); ???????????????h = h < 10 ? ("0" + h) : h; ???????????????m = m < 10 ? ("0" + m) : m; ???????????????s = s < 10 ? ("0" + s) : s; ???????????????document.getElementById("_h").innerHTML = h + "时"; ???????????????document.getElementById("_m").innerHTML = m + "分"; ???????????????document.getElementById("_s").innerHTML = s + "秒"; ???????????????setTimeout(countTime, 1000); ???????????} else { ???????????????document.getElementById("_h").innerHTML = "00时"; ???????????????document.getElementById("_m").innerHTML = "00分"; ???????????????document.getElementById("_s").innerHTML = "00秒"; ???????????} ???????} ???</script>HTML:
<body onload="countTime()"> ???<div class="timer"> ???????<span id="_h"></span> ???????<span id="_m"></span> ???????<span id="_s"></span> ???</div></body>
js简单时分秒倒计时
原文地址：https://www.cnblogs.com/qianxuebing/p/9829434.html