比较精确的js倒计时实现

    // 传入需要倒计时的秒数
    countDown(times) {
      // 时间间隔 1秒
      const interval = 1000;
      // 计算时间，转化为毫秒
      let ms = times * 1000;
      let count = 0;
      const startTime = new Date().getTime();
      const endTime = startTime + ms;
      let timeCounter;
      timeCounter = setTimeout(countDownStart, interval)
      function countDownStart() {
        count++
        const offset = new Date().getTime() - (startTime + count * interval);
        // 计算剩余时间
        const diff = endTime - new Date().getTime();
        const h = Math.floor(diff / (60 * 1000 * 60));
        const hdiff = diff % (60 * 1000 * 60);
        const m = Math.floor(hdiff / (60 * 1000));
        const mdiff = hdiff % (60 * 1000);
        const s = mdiff / (1000);
        const sCeil = Math.ceil(s);
        const sFloor = Math.floor(s);
        let nextTime = interval - offset;
        if (nextTime < 0) {
          nextTime = 0
        }
        ms = ms - interval;
        console.log(`误差：${offset} ms，下一次执行：${nextTime} ms 后，离活动开始还有：${ms} ms`);
        console.log('时：' + h, '分：' + m, '毫秒：' + s, '秒向上取整：' + sCeil)
        if (ms < 0) {
          clearTimeout(timeCounter)
          console.log('此处执行自己想要的操作')
        } else {
          timeCounter = setTimeout(countDownStart, nextTime)
        }
      }
    }

核心代码如上，可以更具自己的业务逻辑修改