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)}}}