JS 实现倒计时

<script>
$(function () {
countdown();
})
function countdown() {
//取到end时间格式 "2016-08-30 13:40:00";
//var endtime = "2016-08-30 13:40:00";
//endtime = endtime.replace(/-/g, "/");
//var end = new Date(endtime);

//取到时间戳 1472538000
var end = new Date(parseInt(1472548000) * 1000);

var now = new Date();
var m = Math.round((end - now) / 1000);
var day = parseInt(m / 24 / 3600);
var hours = parseInt((m % (3600 * 24)) / 3600);
var minutes = parseInt((m % 3600) / 60);
var seconds = m % 60;

if (m < 0) {
document.getElementById("clock").innerHTML = '0天0小时0分';
return;
}
//获取标签 将时间插入标签
document.getElementById("clock").innerHTML = day + "天" + hours + "小时" + minutes + "分";
setTimeout('countdown()', 60000);
}
</script>