react-slip/es/helpers/events.js

Pure React carousel

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.listen = listen;
exports.unlisten = unlisten;
////////////////////////////////////////////////////////////////////////////////////////
// Small helpers that provide an easy and effecient way to add/remove event listeners //
////////////////////////////////////////////////////////////////////////////////////////

var elementsWithListeners = [],
    registeredListeners = [];

function addListener(el, event, cb) {
  var idx = elementsWithListeners.indexOf(el);
  if (idx === -1) {
    idx = elementsWithListeners.length;
    elementsWithListeners.push(el);
    registeredListeners.push({ el: el, totalCount: 0 });
  }

  var listeners = registeredListeners[idx],
      listener = listeners[event];

  if (!listener) {
    listener = listeners[event] = { callbacks: [] };
    listener.cb = function (e) {
      for (var i = 0, l = listener.callbacks.length; i < l; i += 1) {
        listener.callbacks[i](e);
      }
    };
    listeners.totalCount += 1;
    listeners.el.addEventListener(event, listener.cb);
  }

  // just to prevent double listeners
  if (listener.callbacks.indexOf(cb) !== -1) {
    return;
  }

  listener.callbacks.push(cb);
}

function removeListener(el, event, cb) {
  var idx = elementsWithListeners.indexOf(el);
  if (idx === -1) {
    return;
  }

  var listeners = registeredListeners[idx],
      listener = listeners[event],
      callbacks = listener ? listener.callbacks : [];

  if (!listener || callbacks.indexOf(cb) === -1) {
    return;
  }

  callbacks.splice(callbacks.indexOf(cb), 1);
  if (callbacks.length > 0) {
    return;
  }

  listeners.el.removeEventListener(event, listener.cb);
  listeners.totalCount -= 1;
  delete listeners[event];

  if (listeners.totalCount > 0) {
    return;
  }

  elementsWithListeners.splice(idx, 1);
  registeredListeners.splice(idx, 1);
}

/**
 * Subscribe cb to events list
 * @param  {HTMLElement}   el       target element
 * @param  {Array}         events   array of event names
 * @param  {Function} cb   callback that should be called
 */
function listen(el, events, cb) {
  for (var i = 0, l = events.length; i < l; i += 1) {
    addListener(el, events[i], cb);
  }
}

/**
 * Unsubscribe cb from events list
 * @param  {HTMLElement}   el       target element
 * @param  {Array}         events   array of event names
 * @param  {Function} cb   callback that should be unsubscribed
 */

function unlisten(el, events, cb) {
  for (var i = 0, l = events.length; i < l; i += 1) {
    removeListener(el, events[i], cb);
  }
}