API呼び出しに失敗したりタイムアウトしたときに複数回APIをコールするためのラッパー関数

retryFetch.ts

/**
 *
 * @param targetFunc fetch function
 * @param opt retry options
 * @returns
 */
export const retryFetch = <T>(
  targetFunc: () => Promise<T>,
  opt?: {
    retryCount?: number;
    retryTimeout?: number; // seconds
  }
): Promise<T> => {
  return new Promise((resolve, reject) => {
    const retryCount = opt?.retryCount || 3;
    const retryTimeout = opt?.retryTimeout || 10;
    let count = 0;

    // Change intervalId's type to `number | undefined` if you use in browser
    let intervalId: NodeJS.Timeout | undefined = undefined;

    const clearAndResolve = (res: T) => {
      if (intervalId) clearInterval(intervalId);
      resolve(res);
    };

    const clearAndReject = (err: Error) => {
      if (intervalId) clearInterval(intervalId);
      reject(err);
    };

    const intervalFunc = () => {
      count++;
      if (count > retryCount) {
        clearAndReject(new Error('Retry count exceeded'));
      }

      // Repeat unit
      const repeatFunc = () => {
        targetFunc()
          .then((res) => {
            clearAndResolve(res);
          })
          .catch(() => {
            // If error catched, clear interval and start another interval.
            if (intervalId) clearInterval(intervalId);
            intervalFunc();
          });
      };

      // Because the first interval start after retryTimeout seconds,
      // we need to call repeatFunc() once in outside of setInterval().
      repeatFunc();

      // interval start
      intervalId = setInterval(() => {
        count++;
        if (count > retryCount) {
          clearAndReject(new Error('Retry count exceeded'));
        }

        repeatFunc();
      }, retryTimeout * 1000);
    };

    // Start the first interval
    intervalFunc();
  });
};