<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
div {
margin: 200px;
}
span {
display: inline-block;
width: 40px;
height: 40px;
background-color: #333;
font-size: 20px;
color: #fff;
text-align: center;
line-height: 40px;
}
</style>
</head>
<body>
<div>
<span class="hour">1</span>
<span class="minute">2</span>
<span class="second">3</span>
</div>
<script>
var hour = document.querySelector('.hour'); //小时的黑色盒子
var minute = document.querySelector('.minute'); //分钟的黑色盒子
var second = document.querySelector('.second'); //秒数的黑色盒子
var inputtime = +new Date('2019-9-8'); //未来毫秒数
counttime();
setInterval(counttime, 1000); //这个时候时间是每隔一秒改变的
function counttime() { //这个时间是不动的
var time1 = +new Date(); //当前毫秒数
var time = (inputtime - time1) / 1000; // 差值/1000=秒;
var h = parseInt(time / 60 / 60); //时 因为没有天数，所以不用%24
h = h < 10 ? '0' + h : h;
hour.innerHTML = h;
var m = parseInt(time / 60 % 60);
m = m < 10 ? '0' + m : m;
minute.innerHTML = m;
var s = parseInt(time % 60);
s = s < 10 ? '0' + s : s;
second.innerHTML = s;
}
</script>
</body>
</html>
