倒计时效果：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>倒计时效果</title>
</head>
<body>
<div>倒计时：<span id="show"></span></div>
<script>
setInterval(function() {
var endTime = new Date('2020/9/15,00:00:00');//设置结束时间
var curTime = new Date();
var leftTime = parseInt((endTime.getTime() - curTime.getTime()) / 1000);//得出秒
// console.log(leftTime);
var date = parseInt(leftTime / (24 * 60 * 60));
var hours = parseInt(leftTime / (60 * 60) % 24);
var minutes = parseInt(leftTime / 60 % 60);
var seconds = parseInt(leftTime % 60);
var show = document.getElementById('show');
show.innerHTML = date + '天' + hours + '小时' + minutes + '分钟' + seconds + '秒';
}, 1);
</script>
</body>
</html>