Retry a promise until succeed or reach max retry count

retry_promise.js

/**
 * Retry a promise until succeed or reach max retry count.
 *
 * Options includes:
 * - maxRetryCount:
 *   If -1 -> retry until success. Terminate if exceed max count.
 *   If  0 -> No retry
 *   Default: -1
 *
 * - retryPeriod: Timer period. Default: 3 seconds;
 * 
 * @author ntd251
 * @param  {function} requestFn - Function that returns the targeted promise
 * @param  {hash} options - Configuration
 * @return {promise}
 * @example
 * ```js
 * let requestFn = () => {
 *   return new Promise((resolve, reject) => {
 *     $.ajax({
 *       ...,
 *       success: resolve,
 *       error: reject,
 *     });
 *   });
 * };
 *
 * // Retry until success
 * //
 * retryPromise(requestFn);
 *
 * // Retry maximum 3 times, with 1 second interval
 * //
 * retryPromise(requestFn, {
 *   retryPeriod: 1000,
 *   maxRetryCount: 3,
 * });
 *
 * // Do not retry... errhhh I'm not sure if this would ever be used.
 * // similar to `requestFn()`
 * //
 * retryPromise(requestFn, {
 *   maxRetryCount: 0,
 * });
 * ```
 */
function retryPromise(requestFn, options) {
  options = options || {};
  /**
   * By default, retry until success
   */
  let maxRetryCount = options.maxRetryCount;

  if (typeof options.maxRetryCount === 'undefined') {
    maxRetryCount = -1;
  }

  let retryPeriod = options.retryPeriod || 3000;

  let retryCount = 0;
  let loading = false;
  let error;
  let timer;

  let terminateTimer = () => {
    window.clearInterval(timer);
  };

  return new Promise((resolve, reject) => {
    let sendRequest = () => {
      loading = true;

      requestFn().then((response) => {
        /**
         * Resolve and terminate
         */
        resolve(response);
        terminateTimer();
      }, (error) => {
        if (maxRetryCount >= 0 && retryCount >= maxRetryCount) {
          /**
           * Reject and terminate
           * If maxRetryCount = 0. Immediately reject and terminate.
           */
          reject(error);
          terminateTimer();
        } else {
          /**
           * Continue
           */
          retryCount++;
        }
      }).finally(() => {
        loading = false;
      });
    };

    timer = window.setInterval(() => {
      if (!loading) {
        sendRequest();
      }
    }, retryPeriod);

    sendRequest();
  });
}