js时间转换，国际时间

var date = getLocalTime(-8).getDate() //获取日期--西八区，单双日分开做a/b test
if(date % 2 === 0){
   var myTimer = null;
   var countdown = document.getElementById("countdown");
   var currentTimes = parseInt(new Date().getTime() / 1000) ;
   var endTimes = parseInt(new Date().getTime() / 1000 + 1200)

   if(localStorage.getItem('endTimes')){ //有了存储，拿出来减去当前时间的秒数，得到剩余的时间
      var endT = Number(localStorage.getItem('endTimes'));
      var time = Number(endT - currentTimes);
      startTime(time)
   }else{
      localStorage.setItem('endTimes',endTimes) //初次进来，存入未来20分钟的秒数，减去当前的秒 = 20分钟
      startTime(Number(localStorage.getItem('endTimes')) - currentTimes)
   }
}

function startTime(times) {
   if (times >= 0) {
      document.getElementsByClassName("countdown-checkout")[0].style.display = 'block';
      localStorage.setItem('countdown', times)
      myTimer = setInterval(function () {
         var leftTime = Number(localStorage.getItem('countdown'));
         var minute = parseInt(leftTime / 60);
         var second = parseInt(leftTime % 60);
         var leftMinute = minute <= 9 ? '0' + minute : minute;
         var leftSecond = second <= 9 ? '0' + second : second;
         countdown.innerHTML = leftMinute + ':' + leftSecond;
         leftTime--;
         if (leftTime < -1) {
            clearInterval(myTimer);
            document.getElementsByClassName("countdown-checkout")[0].style.display = 'none';
         } else {
            localStorage.setItem('countdown', leftTime)
         }
      }, 1000);
   }
}

function getLocalTime(i) { // i 是时区，比如 -8
   if (typeof i !== 'number') return;
   var d = new Date();
   var len = d.getTime();
   var offset = d.getTimezoneOffset() * 60000;
   var utcTime = len + offset;
   return new Date(utcTime + 3600000 * i);
}