function FreshTime()
{
        var endtime=new Date("2017/9/30,18:05:00");//結束時間
        var nowtime = new Date();//當前時間
        var lefttime=parseInt((endtime.getTime()-nowtime.getTime())/1000); 
        d=parseInt(lefttime/3600/24);
        h=parseInt((lefttime/3600)%24);
        m=parseInt((lefttime/60)%60);
        s=parseInt(lefttime%60);
        document.getElementById(
 
"LeftTime").innerHTML=d+"天"+h+"小時"+m+"分"+s+"秒";
}
FreshTime()
var sh;
sh=setInterval(FreshTime,1000);

js倒計時效果