JavaScript-时间倒计时

<script>
var timer;
countDown=function(){
timer=window.setInterval(function(){
ShowCountDown(2016,3,15);
}, 1000);
//clearInterval(timer);
}
function ShowCountDown(year,month,day)
{
var now = new Date();
var endDate = new Date(year, month-1, day);
var leftTime=endDate.getTime()-now.getTime();
var leftsecond = parseInt(leftTime/1000);
var day1=Math.floor(leftsecond/(60*60*24));
var hour=Math.floor((leftsecond-day1*24*60*60)/3600);
var minute=Math.floor((leftsecond-day1*24*60*60-hour*3600)/60);
var second=Math.floor(leftsecond-day1*24*60*60-hour*3600-minute*60);
console.log(year+"年"+month+"月"+day+"日还有："+day1+"天"+hour+"小时"+minute+"分"+second+"秒");
}
</script>