jQuery 实现倒计时天,时,分,秒功能

<span class="joind">135</span>天<span class="joinh">7</span>时<span class="joinm">46</span>分<span class="joins">25</span>秒 

<script src="https://code.jquery.com/jquery-3.1.1.min.js" type="text/javascript" charset="utf-8"></script>
<script type="text/javascript">
 var setTimer = null;
 var chazhi = 0;
 //差值计算
 //例子(模拟)
 chazhi = 135 * 86400000;
 //真实时间(注意月份需减掉1，否则时间会计算错误)
 //chazhi = (new Date(year,month-1,day,hour,minute,second)) - (new Date()); //计算剩余的毫秒数
 //chazhi = (new Date(2018,8-1,6,6,6,6)) - (new Date());
 
 //执行函数部分
 countFunc(chazhi);
 setTimer = setInterval(function() {
 chazhi = chazhi - 1000;
 countFunc(chazhi);
 }, 1000);
 function countFunc(leftTime) {
 if(leftTime >= 0) {
 var days = parseInt(leftTime / 1000 / 60 / 60 / 24, 10); //计算剩余的天数 
 var hours = parseInt(leftTime / 1000 / 60 / 60 % 24, 10); //计算剩余的小时 
 var minutes = parseInt(leftTime / 1000 / 60 % 60, 10); //计算剩余的分钟 
 var seconds = parseInt(leftTime / 1000 % 60, 10); //计算剩余的秒数 
 days = checkTime(days);
 hours = checkTime(hours);
 minutes = checkTime(minutes);
 seconds = checkTime(seconds);
 $(".joind").html(days);
 $(".joinh").html(hours);
 $(".joinm").html(minutes);
 $(".joins").html(seconds);
 } else {
 clearInterval(setTimer);
 $(".joind").html("00");
 $(".joinh").html("00");
 $(".joinm").html("00");
 $(".joins").html("00");
 }
 }
 function checkTime(i) { //将0-9的数字前面加上0，例1变为01 
 if(i < 10) {
 i = "0" + i;
 }
 return i;
 }
</script>