JavaScript倒计时实现

 /**
  * 倒计时函数
  * @param {String}} endTime 终止时间戳
  */
 const countDown = (endTime, callback) => {
     const end = endTime,
         now = new Date().getTime();
     let differ = end - now,
         hours, minutes, seconds;
     if (differ >= 0) {
         hours = Math.floor(differ / 1000 / 60 / 60 % 24);
         minutes = Math.floor(differ / 1000 / 60 % 60);
         seconds = Math.floor(differ / 1000 % 60);
     }
     callback({
         h: check(hours),
         m: check(minutes),
         s: check(seconds)
     });
     setTimeout(() => {
         countDown(end, callback);
     }, 1000);
 };

 /**
  * 时间前加零
  * @param {Number} time
  */
 const check = time => {
     if (time < 10) {
         time = '0' + time;
     }
     return time.toString();
 };

 export default countDown;

 countDown(new Date('2018/9/5 10:00:00'), function(timeObj) { // 调用
       console.log(timeObj.h, timeObj.m, timeObj.s)
 });