countTime(){
    var that = this;
    var timer = setInterval(() => {
      var canbuy=that.data.can_buy;
      var date = new Date();
      var now = date.getTime();
      var endDate = new Date(that.data.expirtime);//设置截止时间
      var end = endDate.getTime();
      var leftTime = end - now; //时间差                              
      var m, s, ms;
      if (leftTime > 0) {
        m = Math.floor(leftTime / 1000 / 60 % 60);
        s = Math.floor(leftTime / 1000 % 60);
        ms = Math.floor(leftTime % 1000);
        ms = ms < 100 ? "0" + ms : ms
        s = s < 10 ? "0" + s : s
        m = m < 10 ? "0" + m : m
        canbuy=true
      } else {
        canbuy=false
        m=0
        s=0
        ms=0
      }
      m==0?'00':m,
      s==0?'00':s,
      that.setData({
        countdownTime:m+':'+s,
        can_buy:canbuy
      })
      if(!canbuy){
        clearInterval(timer)
      }
    }, 500)
  }

上线之后iphone11、iphone12倒计时都无效，用setTimeout函数也无效