grouped-queue/lib/subqueue.js

In memory queue system prioritizing tasks

"use strict";
module.exports = SubQueue;

function isPromise(obj) {
  return (
    !!obj &&
    (typeof obj === "object" || typeof obj === "function") &&
    typeof obj.then === "function"
  );
}

function SubQueue() {
  this.__queue__ = [];
}

/**
 * Add a task to this queue
 * @param  {Function} task
 */

SubQueue.prototype.push = function (task, opt) {
  opt = opt || {};

  // Don't register named task if they're already planned
  if (opt.once && this.__queue__.find((queue) => queue.name === opt.once)) {
    return;
  }

  this.__queue__.push({ task: task, name: opt.once });
};

/**
 * Return the first entry of this queue
 * @return {Function} The first task
 */

SubQueue.prototype.shift = function () {
  return this.__queue__.shift();
};

/**
 * Run task
 * @param  {Function} skip  Callback if no task is available
 * @param  {Function} done  Callback once the task is completed
 */

SubQueue.prototype.run = function (skip, done, stop) {
  if (this.__queue__.length === 0) return skip();
  setImmediate(() => {
    var result;
    try {
      result = this.shift().task.call(null, done, stop);
    } catch (error) {
      stop(error);
    }
    if (isPromise(result)) {
      result.catch((error) => stop(error));
    }
  });
};