chrome/browser/resources/chromeos/arc_support/event_tracker.js

// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/**
 * @fileoverview EventTracker is a simple class that manages the addition and
 * removal of DOM event listeners. In particular, it keeps track of all
 * listeners that have been added and makes it easy to remove some or all of
 * them without requiring all the information again. This is particularly handy
 * when the listener is a generated function such as a lambda or the result of
 * calling Function.bind.
 */

cr.define('cr', function() {
  /* #export */ class EventTracker {
    /**
     * Create an EventTracker to track a set of events.
     * EventTracker instances are typically tied 1:1 with other objects or
     * DOM elements whose listeners should be removed when the object is
     * disposed or the corresponding elements are removed from the DOM.
     */
    constructor() {
      /**
       * @type {Array<EventTrackerEntry>}
       * @private
       */
      this.listeners_ = [];
    }

    /**
     * Add an event listener - replacement for EventTarget.addEventListener.
     * @param {!EventTarget} target The DOM target to add a listener to.
     * @param {string} eventType The type of event to subscribe to.
     * @param {EventListener|Function} listener The listener to add.
     * @param {boolean=} capture Whether to invoke during the capture phase.
     */
    add(target, eventType, listener, capture = false) {
      const h = {
        target: target,
        eventType: eventType,
        listener: listener,
        capture: capture,
      };
      this.listeners_.push(h);
      target.addEventListener(eventType, listener, capture);
    }

    /**
     * Remove any specified event listeners added with this EventTracker.
     * @param {!EventTarget} target The DOM target to remove a listener from.
     * @param {?string} eventType The type of event to remove.
     */
    remove(target, eventType) {
      this.listeners_ = this.listeners_.filter(listener => {
        if (listener.target === target &&
            (!eventType || (listener.eventType === eventType))) {
          EventTracker.removeEventListener(listener);
          return false;
        }
        return true;
      });
    }

    /** Remove all event listeners added with this EventTracker. */
    removeAll() {
      this.listeners_.forEach(
          listener => EventTracker.removeEventListener(listener));
      this.listeners_ = [];
    }

    /**
     * Remove a single event listener given it's tracking entry. It's up to the
     * caller to ensure the entry is removed from listeners_.
     * @param {EventTrackerEntry} entry The entry describing the listener to
     * remove.
     */
    static removeEventListener(entry) {
      entry.target.removeEventListener(
          entry.eventType, entry.listener, entry.capture);
    }
  }

  /**
   * The type of the internal tracking entry.
   * @typedef {{target: !EventTarget,
   *            eventType: string,
   *            listener: (EventListener|Function),
   *            capture: boolean}}
   */
  let EventTrackerEntry;

  // #cr_define_end
  console.warn('crbug/1173575, non-JS module files deprecated.');
  return {EventTracker};
});