js倒计时

function timer()
{
var ts = (new Date(2018, 11, 11, 9, 0, 0)) - (new Date());//计算剩余的毫秒数
var dd = parseInt(ts / 1000 / 60 / 60 / 24, 10);//计算剩余的天数
var hh = parseInt(ts / 1000 / 60 / 60 % 24, 10);//计算剩余的小时数
var mm = parseInt(ts / 1000 / 60 % 60, 10);//计算剩余的分钟数
var ss = parseInt(ts / 1000 % 60, 10);//计算剩余的秒数
dd = checkTime(dd);
hh = checkTime(hh);
mm = checkTime(mm);
ss = checkTime(ss);
document.getElementById("leftTime").innerHTML = dd + "天" + hh + "时" + mm + "分" + ss + "秒";
setInterval("timer()",1000);
}
function checkTime(i)
{
if (i < 10) {
i = "0" + i;
}
return i;
}