Implementation of a processOne function to process a single item in the queue

Queue.prototype.processOne.js

const Queue = require("bull");
const Job = Queue.Job;

/**
 * Process only one queue at a time
 * Bull has not implimented this feature
 * @param callback {function(Object)} This will be called after pulling a job from the queue.
 * A job will be passed as the first parameter
 *
 * @return {Object} The information about the next Job that is in the queue
 *
 * https://github.com/OptimalBits/bull/blob/master/PATTERNS.md#manually-fetching-jobs
 * @since: 20200227
 *
 * If callback returns an Error , flag the job as failed
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error
 */

if (typeof Queue.prototype.processOne !== "function") {
  Queue.prototype.processOne = function (callback) {
    return new Promise(async (resolve, reject) => {
      //Pull a job from 'waiting' and move it to 'active'.
      await this.isReady();
      const job = await this.getNextJob();

      if (job) {
        return callback(job)
          .then(async (data) => {
            await this.isReady();
            //Move the job to the 'completed' queue.
            const [nextJobData, nextJobId] =
              (await job.moveToCompleted("succeeded", true)) || [];

            let nextJob;
            if (nextJobData) {
              nextJob = Job.fromJSON(this, nextJobData, nextJobId);
            }

            return resolve(nextJob);
          })
          .catch((error) => {
            //Move the job to the 'failed' queue if something goes wrong.
            job.moveToFailed(
              {
                message: error.message,
              },
              true
            );

            return reject(error);
          });
      } else {
        return resolve();
      }
    });
  };
}
module.exports = Queue;