promise retry

retry.ts

export function retryPromise<T>(fn: () => Promise<T>, retriesLeft = 5, interval = 375): Promise<T> {
  return new Promise((resolve, reject) => {
    fn()
      .then(resolve)
      .catch(error => {
        setTimeout(() => {
          if (retriesLeft === 1) {
            // reject('maximum retries exceeded');
            reject(error);
            return;
          }

          // math formula (375 2^(5 - n)) -> it allows to increase request timeout, like 375, 750, 1500, 3000, 6000.
          // Math.max safeguard is here to make sure that we do not reach backoff values below 375ms.
          const timeout = Math.max(375 * 2 ** (5 - retriesLeft), 300, 375);
          // Passing on "reject" is the important part
          retryPromise(fn, retriesLeft - 1, timeout).then(resolve, reject);
        }, interval);
      });
  });
}