React实现一个倒计时hook组件实战示例

export interface CountDownOptions {
  
  deadlineTime: number;
  
  showMillisecond?: boolean;
}

export interface TimeInfo {
  
  day: number;
  
  hours: number;
  
  hoursStr: string;
  
  minutes: number;
  
  minutesStr: string;
  
  seconds: number;
  
  secondsStr: string;
  
  milliseconds?: number;
  
  millisecondsStr?: string;
  
  end: boolean;
}

{
    day,
    hours,
    hoursStr,
    minutes,
    minutesStr,
    seconds,
    secondsStr,
    end: false,
  }

// 格式化数据，这里就是补零
function fORMate(time: number): string {
  return `${time < 10 ? "0" : ""}${time}`;
}

function clearCountdownInfo(showMillisecond = false): TimeInfo {
  const timeInfo: TimeInfo = {
    day: 0,
    hours: 0,
    hoursStr: "00",
    minutes: 0,
    minutesStr: "00",
    seconds: 0,
    secondsStr: "00",
    end: true,
  };
  if (showMillisecond) {
    timeInfo.milliseconds = 0;
    timeInfo.millisecondsStr = "0";
  }
  return timeInfo;
}

function computeCountdownInfo(
  remainTime: number,
  showMillisecond = false
): TimeInfo {
  // 剩余时间小于说明结束，直接清空
  if (remainTime < 0) {
    return clearCountdownInfo(showMillisecond);
  }
  // 这里用了一个比较笨的方法，一个个进行计算，后续可以优化试试看
  const day = Math.floor(remainTime / (24 * 60 * 60));
  const hours = Math.floor((remainTime / (60 * 60)) % 24);
  const hoursStr = formate(hours);
  const minutes = Math.floor((remainTime / 60) % 60);
  const minutesStr = formate(minutes);
  const seconds = Math.floor(remainTime % 60);
  const secondsStr = formate(seconds);
  // 组合成需要返回的时间信息
  const timeInfo: TimeInfo = {
    day,
    hours,
    hoursStr,
    minutes,
    minutesStr,
    seconds,
    secondsStr,
    end: false,
  };
  // 需要显示毫秒逻辑处理
  if (showMillisecond) {
    const milliseconds = Math.floor(remainTime * 1000);
    // 只取首位
    const millisecondsStr = String(milliseconds).slice(-3);
    timeInfo.milliseconds = milliseconds;
    timeInfo.millisecondsStr = millisecondsStr;
  }
  return timeInfo;
}

export const useCountdown = (options: CountDownOptions) => {
  // 首次初始化数据，显示清除的数据
  const [timeInfo, setTimeInfo] = useState<TimeInfo>(
    clearCountdownInfo(options.showMillisecond)
  );
  useEffect(() => {
    let timer = 0;
    function countdown() {
      const remainTime = computeRemainTime(options.deadlineTime);
      // 剩余时间大于 0 才开始倒计时
      if (remainTime > 0) {
        // 未结束时直接定时下一次在执行判断 countdown
        timer = window.setTimeout(
          countdown,
          options.showMillisecond ? 100 : 1000 // 毫秒级则修改定时器时间
        );
      }
      const data = computeCountdownInfo(remainTime, options.showMillisecond);
      setTimeInfo(data);
    }
    // 开始倒计时
    countdown();
    return () => {
      // 清除定时器
      timer && clearInterval(timer);
    };
  }, [options.deadlineTime, options.showMillisecond]);
  return timeInfo;
};

// 渲染时获取一次剩余时间
const remainTime = useMemo(
    () => computeRemainTime(options.deadlineTime),
    [options.deadlineTime]
);
// 首次初始化数据，以防页面闪烁
const [timeInfo, setTimeInfo] = useState<TimeInfo>(
    computeCountdownInfo(remainTime)
);