<h1 id="h3"></h1>
<script>
time('2020,10,1 00:00:00');
setInterval(function () {
time('2020,10,1 00:00:00');
}, 1000)
function time(n) {
var current = new Date();
var future = new Date(n);
var gap = parseInt((future - current) / 1000);
var day = parseInt(gap / 3600 / 24)
var hour = parseInt(gap / 3600 % 24);
var min = parseInt(gap % 3600 / 60);
var sec = gap % 60;
h3.innerHTML = '距离国庆还剩' + day + '天' + hour + '小时' + min + '分钟' + sec + '秒';
}
</script>