简单的倒计时

 countDown = () => {
    const { placeOrderTime, interval } = this.state
    const startTime = placeOrderTime;//下单时的时间戳
    const stopTime = new Date().getTime()//当前时间时间戳
    const cTime = stopTime - startTime

    //大于15分钟之后设置订单状态为失效
    if (cTime > 15 * 60 * 1000) {
      clearInterval(interval)
      this.setState({
        payStatus: PayStatus.已失效
      })
      return
    }
    //将时间戳差值转化为分钟数和秒数
    const modeData = cTime % 1000;
    const totalMinute = (cTime - modeData) / 1000//总秒数
    const differMinuteTime = 15 * 60 - totalMinute//距离15分钟剩余的时间秒

    //获取倒计时分秒数的个位，十位数字
    const countDownTimeSecond = differMinuteTime % 60
    const countDownTimeMinute = (differMinuteTime - countDownTimeSecond) / 60
    const minuteIndividual = countDownTimeMinute % 10
    const minuteTen = (countDownTimeMinute - minuteIndividual) / 10
    const secondIndividual = countDownTimeSecond % 10
    const secondTen = (countDownTimeSecond - secondIndividual) / 10
    this.setState({
      countDownTime: {
        minuteIndividual,
        minuteTen,
        secondIndividual,
        secondTen,
      }
    })
  }