js倒计时

 1 <div class="nlpz_sjdjs">剩余：<span>00</span>:<span>00</span>:<span>00</span></div>
 2 
 3 <script type="text/javascript">
 4     var starttime = new Date("2018-03-09 15:44:00");
 5     function tt(){
 6         var nowtime = new Date();
 7         //alert(nowtime);
 8         var time = starttime - nowtime;
 9         var day = parseInt(time / 1000 / 60 / 60 / 24);//天
10         var hour = parseInt(time / 1000 / 60 / 60 % 24);//小时
11         var minute = parseInt(time / 1000 / 60 % 60);//分钟
12         var seconds = parseInt(time / 1000 % 60);//秒
13         
14         if(hour<=0 && minute<=0 && seconds<=0){
15             clearInterval(sj);
16             $('.nlpz_sjdjs').html("活动已结束");
17         }else{
18             $('.nlpz_sjdjs').html('剩余'+day+'天:'+'<span>'+hour+'</span>'+':'+'<span>'+minute+'</span>'+':'+'<span>'+seconds+'</span>');
19         } 
20     }
21     var sj = setInterval(function () {tt();}, 1000);
22 </script>
注意引入jquery