倒计时
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<h1>倒计时:<div id="djs"></div>
</h1>
<script>
var djs = document.getElementById("djs")
setInterval(function countDown() {
var nowTime = +new Date();
var futureTime = +new Date('2020-04-02 23:20:00');
var times = (futureTime - nowTime) / 1000;
var d = parseInt(times / 60 / 60 / 24);
d = d < 10 ? '0' + d : d;
var h = parseInt(times / 60 / 60 % 24);
h = h < 10 ? '0' + h : h;
var m = parseInt(times / 60 % 60);
m = m < 10 ? '0' + m : m;
var s = parseInt(times % 60);
s = s < 10 ? '0' + s : s;
var t = d + '天' + h + '时' + m + '分' + s + '秒';
document.getElementById("djs").innerHTML = t;
}, 500);
</script>
</body>
</html>
当前时间
<body>
<div id="Date"></div>
<script type="text/javascript">
setInterval(function(){
var date = new Date();
var year = date.getFullYear(); //获取当前年份
var mon = date.getMonth()+1; //获取当前月份
var da = date.getDate(); //获取当前日
var day = date.getDay(); //获取当前星期几
var h = date.getHours(); //获取小时
var m = date.getMinutes(); //获取分钟
var s = date.getSeconds(); //获取秒
var d = document.getElementById('Date');
d.innerHTML='当前时间:'+year+'年'+mon+'月'+da+'日'+'星期'+day+' '+h+':'+m+':'+s;
},1000)
</script>