js实现页面多个日期时间倒计时效果

<style>
  .mytime{ line-height: 40px; width: 300px; margin: 0 auto;}
 </style>

<div class="mytime jsTime" data-time="2019-04-01 16:58:00">时间1</div>
<div class="mytime jsTime" data-time="2019-04-04 18:00:02">时间2</div>
<div class="mytime jsTime" data-time="2019-04-05 19:01:31">时间3</div>
<div class="mytime jsTime" data-time="2019-04-06 05:05:15">时间4</div>
<div class="mytime jsTime" data-time="2019-04-07 09:01:43">时间5</div>
<hr>
<div class="mytime jsTime2" data-time="2019-04-08 16:30:05">时间1</div>
<div class="mytime jsTime2" data-time="2019-04-09 14:01:22">时间2</div>
<div class="mytime jsTime2" data-time="2019-04-10 18:06:25">时间3</div>
<div class="mytime jsTime2" data-time="2019-04-11 22:07:19">时间4</div>
<div class="mytime jsTime2" data-time="2019-04-12 23:12:38">时间5</div>

<!-- 方法1 -->
<script>
 const countdown = {
  domList : document.querySelectorAll('.jsTime'),
  formatNumber(n){
   // return n.toString().padStart(2, '0'); // 用padStart方法要注意兼容问题
   n = n.toString();
   return n[1] ? n : '0' + n;
  },
  setTime(dom){
   //获取设置的时间 如：2019-3-28 14:00:00 ios系统得加正则.replace(/\-/g, '/');
   const leftTime = new Date(dom.getAttribute('data-time').replace(/\-/g, '/')) - new Date();
   if (leftTime >= 0) {
    const d = Math.floor(leftTime / 1000 / 60 / 60 / 24);
    const h = Math.floor(leftTime / 1000 / 60 / 60 % 24);
    const m = Math.floor(leftTime / 1000 / 60 % 60);
    const s = Math.floor(leftTime / 1000 % 60);
    dom.innerHTML = `剩余${ d > 0 ? d + '天' : '' }${ [h, m, s].map(this.formatNumber).join(':') }`;
   } else {
    clearInterval(dom.$timer);
    dom.innerHTML = '拼团已结束';
   }
  },
  start(){
   this.domList.forEach((dom) => {
    this.setTime(dom);
    dom.$timer = setInterval(() => {
     this.setTime(dom);
    }, 1e3);
   });
  },
 };
 countdown.start();
</script>

<!-- 方法2 -->
<script>
 //时间格式处理
 const formatNumber = n => {
 n = n.toString();
 return n[1] ? n : '0' + n;
 };
 //团购倒计时
 const teamCountTime = (obj) => {
 var timer = null;
 function fn(){
  //获取设置的时间 如：2019-3-28 14:00:00 ios系统得加正则.replace(/\-/g, '/');
  var setTime = obj.getAttribute('data-time').replace(/\-/g, '/');
  //获取当前时间
  var date = new Date(),
   now  = date.getTime(),
   endDate = new Date(setTime),
   end  = endDate.getTime();
  //时间差
  var leftTime = end - now;
  //d,h,m,s 天时分秒
  var d, h,m,s;
  var otime = '';
  if (leftTime >= 0) {
  d = Math.floor(leftTime / 1000 / 60 / 60 / 24);
  h = Math.floor(leftTime / 1000 / 60 / 60 % 24);
  m = Math.floor(leftTime / 1000 / 60 % 60);
  s = Math.floor(leftTime / 1000 % 60);
  if (d <= 0) {
   otime = [h, m, s].map(formatNumber).join(':');
  } else {
   otime = d + '天' + [h, m, s].map(formatNumber).join(':');
  }
  obj.innerHTML = '剩余' + otime;
  //
  timer = setTimeout(fn, 1e3);
  } else {
  clearTimeout(timer);
  obj.innerHTML = '拼团已结束';
  }
 }
 fn();
 };
 let jsTimes = document.querySelectorAll('.jsTime2');
 jsTimes.forEach((obj) => {
 teamCountTime(obj);
 });
</script>