elasticlunr/lib/event_emitter.js

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/*!
 * elasticlunr.EventEmitter
 * Copyright (C) @YEAR Oliver Nightingale
 * Copyright (C) @YEAR Wei Song
 */

/**
 * elasticlunr.EventEmitter is an event emitter for elasticlunr.
 * It manages adding and removing event handlers and triggering events and their handlers.
 *
 * Each event could has multiple corresponding functions,
 * these functions will be called as the sequence that they are added into the event.
 * 
 * @constructor
 */
elasticlunr.EventEmitter = function () {
  this.events = {};
};

/**
 * Binds a handler function to a specific event(s).
 *
 * Can bind a single function to many different events in one call.
 *
 * @param {String} [eventName] The name(s) of events to bind this function to.
 * @param {Function} fn The function to call when an event is fired.
 * @memberOf EventEmitter
 */
elasticlunr.EventEmitter.prototype.addListener = function () {
  var args = Array.prototype.slice.call(arguments),
      fn = args.pop(),
      names = args;

  if (typeof fn !== "function") throw new TypeError ("last argument must be a function");

  names.forEach(function (name) {
    if (!this.hasHandler(name)) this.events[name] = [];
    this.events[name].push(fn);
  }, this);
};

/**
 * Removes a handler function from a specific event.
 *
 * @param {String} eventName The name of the event to remove this function from.
 * @param {Function} fn The function to remove from an event.
 * @memberOf EventEmitter
 */
elasticlunr.EventEmitter.prototype.removeListener = function (name, fn) {
  if (!this.hasHandler(name)) return;

  var fnIndex = this.events[name].indexOf(fn);
  if (fnIndex === -1) return;

  this.events[name].splice(fnIndex, 1);

  if (this.events[name].length == 0) delete this.events[name];
};

/**
 * Call all functions that bounded to the given event.
 *
 * Additional data can be passed to the event handler as arguments to `emit`
 * after the event name.
 *
 * @param {String} eventName The name of the event to emit.
 * @memberOf EventEmitter
 */
elasticlunr.EventEmitter.prototype.emit = function (name) {
  if (!this.hasHandler(name)) return;

  var args = Array.prototype.slice.call(arguments, 1);

  this.events[name].forEach(function (fn) {
    fn.apply(undefined, args);
  }, this);
};

/**
 * Checks whether a handler has ever been stored against an event.
 *
 * @param {String} eventName The name of the event to check.
 * @private
 * @memberOf EventEmitter
 */
elasticlunr.EventEmitter.prototype.hasHandler = function (name) {
  return name in this.events;
};