strudel/src/util/eventEmitter.js

A front-end framework for back-end powered web.

import { isFunction } from './helpers';
import handleError from './error';

/**
 * Event listeners
 * @type {{}}
 */
const events = {};

/**
 * @classdesc Simple Event Emitter implementation - global
 * @class
 */
class EventEmitter {
  static getEvents() {
    return events;
  }

  static removeAllListeners() {
    Object.keys(events).forEach((prop) => {
      delete events[prop];
    });
  }

  /**
   * Add event listener to the map
   * @param {string} label
   * @param {Function} callback
   */
  $on(label, callback) {
    if (!events[label]) {
      events[label] = [];
    }
    events[label].push(callback);
  }

  /**
   * Remove event listener from registry
   * @param {string} label
   * @param {Function} callback
   * @returns {boolean}
   */
  $off(label, callback) {
    const listeners = events[label];

    if (listeners && listeners.length) {
      const index = listeners.reduce((i, listener, ind) => {
        return (isFunction(listener) && listener === callback) ? i = ind : i;
      }, -1);

      if (index > -1) {
        listeners.splice(index, 1);
        events[label] = listeners;
        return true;
      }
    }
    return false;
  }

  /**
   * Notifies listeners attached to event
   * @param {string} label
   * @param args
   * @returns {boolean}
   */
  $emit(label, ...args) {
    const listeners = events[label];

    if (listeners && listeners.length) {
      try {
        listeners.forEach((listener) => {
          listener(...args);
        });
      } catch (e) {
        handleError(e, this.constructor, 'event handler');
      }
      return true;
    }
    return false;
  }
}

export default EventEmitter;