pending-queue/lib/index.js

pending-queue ensures a certain asynchronous method only run once, and queues listeners which are registered to it.

'use strict';

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _toConsumableArray(arr) { if (Array.isArray(arr)) { for (var i = 0, arr2 = Array(arr.length); i < arr.length; i++) { arr2[i] = arr[i]; } return arr2; } else { return Array.from(arr); } }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

var _require = require('events'),
    EventEmitter = _require.EventEmitter;

var assert = require('assert');

module.exports = function (_EventEmitter) {
  _inherits(Queue, _EventEmitter);

  function Queue(options) {
    _classCallCheck(this, Queue);

    var _this = _possibleConstructorReturn(this, (Queue.__proto__ || Object.getPrototypeOf(Queue)).call(this));

    _this._stringify = JSON.stringify;

    _this.setMaxListeners(0);

    assert(Object(options) === options, 'options must be an object');

    var load = options.load,
        stringify = options.stringify;

    assert(typeof load === 'function', 'options.load must be a function');
    _this._load = load;

    if (stringify) {
      _this._stringify = stringify;
    }
    return _this;
  }

  _createClass(Queue, [{
    key: 'add',
    value: function add() {
      var stringify = this._stringify;

      for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
        args[_key] = arguments[_key];
      }

      return this._add(stringify(args), args);
    }
  }, {
    key: 'addWithKey',
    value: function addWithKey(key) {
      for (var _len2 = arguments.length, args = Array(_len2 > 1 ? _len2 - 1 : 0), _key2 = 1; _key2 < _len2; _key2++) {
        args[_key2 - 1] = arguments[_key2];
      }

      return this._add(key, args);
    }
  }, {
    key: '_add',
    value: function _add(key, args) {
      var _this2 = this;

      return new Promise(function (resolve, reject) {
        _this2._run(key, args, function (err, data) {
          if (err) {
            return reject(err);
          }

          resolve(data);
        });
      });
    }
  }, {
    key: '_run',
    value: function _run(key, args, callback) {
      var _this3 = this;

      this.on(key, callback);
      if (this.listenerCount(key) !== 1) {
        return;
      }

      // Avoid load method to access the context of pending-queue
      var load = this._load;
      Promise.resolve(load.apply(undefined, _toConsumableArray(args))).then(function (data) {
        _this3.emit('load', key, data);
        _this3.emit(key, null, data);
        _this3.removeAllListeners(key);
      }, function (err) {
        _this3.emit(key, err);
        _this3.removeAllListeners(key);
      });
    }
  }]);

  return Queue;
}(EventEmitter);