BackboneEvents.js

/*
  Extracted from Backbone.js 1.3.3
  This allows the use of Backbone.Events without having to load the entirety of Backbone.
  Reason: The Backbone.Events system is more versatile than jQuery Custom Events and this
          provides a smaller footprint than loading the entire Backbone.js file or the
          unnecessary functions listed below.
  Functions Included: on, off, trigger
  Functions NOT Included: listenTo, stopListening, once, listenToOnce
*/

// We create an empty function called Backbone so we can attach the Events to it as we would
// if we were using Backbone.js in its entirety.
var Backbone = function(){};

/*
  Everything below this point is direct from Backbone.js 1.3.3, including the comments
*/

  // Backbone.Events
  // ---------------

  // A module that can be mixed in to *any object* in order to provide it with
  // a custom event channel. You may bind a callback to an event with `on` or
  // remove with `off`; `trigger`-ing an event fires all callbacks in
  // succession.
  //
  //     var object = {};
  //     _.extend(object, Backbone.Events);
  //     object.on('expand', function(){ alert('expanded'); });
  //     object.trigger('expand');
  //
  var Events = Backbone.Events = {};

  // Regular expression used to split event strings.
  var eventSplitter = /\s+/;

  // Iterates over the standard `event, callback` (as well as the fancy multiple
  // space-separated events `"change blur", callback` and jQuery-style event
  // maps `{event: callback}`).
  var eventsApi = function(iteratee, events, name, callback, opts) {
    var i = 0, names;
    if (name && typeof name === 'object') {
      // Handle event maps.
      if (callback !== void 0 && 'context' in opts && opts.context === void 0) opts.context = callback;
      for (names = _.keys(name); i < names.length ; i++) {
        events = eventsApi(iteratee, events, names[i], name[names[i]], opts);
      }
    } else if (name && eventSplitter.test(name)) {
      // Handle space-separated event names by delegating them individually.
      for (names = name.split(eventSplitter); i < names.length; i++) {
        events = iteratee(events, names[i], callback, opts);
      }
    } else {
      // Finally, standard events.
      events = iteratee(events, name, callback, opts);
    }
    return events;
  };

  // Bind an event to a `callback` function. Passing `"all"` will bind
  // the callback to all events fired.
  Events.on = function(name, callback, context) {
    return internalOn(this, name, callback, context);
  };

  // Guard the `listening` argument from the public API.
  var internalOn = function(obj, name, callback, context, listening) {
    obj._events = eventsApi(onApi, obj._events || {}, name, callback, {
      context: context,
      ctx: obj,
      listening: listening
    });

    if (listening) {
      var listeners = obj._listeners || (obj._listeners = {});
      listeners[listening.id] = listening;
    }

    return obj;
  };

  // The reducing API that adds a callback to the `events` object.
  var onApi = function(events, name, callback, options) {
    if (callback) {
      var handlers = events[name] || (events[name] = []);
      var context = options.context, ctx = options.ctx, listening = options.listening;
      if (listening) listening.count++;

      handlers.push({callback: callback, context: context, ctx: context || ctx, listening: listening});
    }
    return events;
  };

  // Remove one or many callbacks. If `context` is null, removes all
  // callbacks with that function. If `callback` is null, removes all
  // callbacks for the event. If `name` is null, removes all bound
  // callbacks for all events.
  Events.off = function(name, callback, context) {
    if (!this._events) return this;
    this._events = eventsApi(offApi, this._events, name, callback, {
      context: context,
      listeners: this._listeners
    });
    return this;
  };

  // The reducing API that removes a callback from the `events` object.
  var offApi = function(events, name, callback, options) {
    if (!events) return;

    var i = 0, listening;
    var context = options.context, listeners = options.listeners;

    // Delete all events listeners and "drop" events.
    if (!name && !callback && !context) {
      var ids = _.keys(listeners);
      for (; i < ids.length; i++) {
        listening = listeners[ids[i]];
        delete listeners[listening.id];
        delete listening.listeningTo[listening.objId];
      }
      return;
    }

    var names = name ? [name] : _.keys(events);
    for (; i < names.length; i++) {
      name = names[i];
      var handlers = events[name];

      // Bail out if there are no events stored.
      if (!handlers) break;

      // Replace events if there are any remaining.  Otherwise, clean up.
      var remaining = [];
      for (var j = 0; j < handlers.length; j++) {
        var handler = handlers[j];
        if (
          callback && callback !== handler.callback &&
            callback !== handler.callback._callback ||
              context && context !== handler.context
        ) {
          remaining.push(handler);
        } else {
          listening = handler.listening;
          if (listening && --listening.count === 0) {
            delete listeners[listening.id];
            delete listening.listeningTo[listening.objId];
          }
        }
      }

      // Update tail event if the list has any events.  Otherwise, clean up.
      if (remaining.length) {
        events[name] = remaining;
      } else {
        delete events[name];
      }
    }
    return events;
  };

  // Trigger one or many events, firing all bound callbacks. Callbacks are
  // passed the same arguments as `trigger` is, apart from the event name
  // (unless you're listening on `"all"`, which will cause your callback to
  // receive the true name of the event as the first argument).
  Events.trigger = function(name) {
    if (!this._events) return this;

    var length = Math.max(0, arguments.length - 1);
    var args = Array(length);
    for (var i = 0; i < length; i++) args[i] = arguments[i + 1];

    eventsApi(triggerApi, this._events, name, void 0, args);
    return this;
  };

  // Handles triggering the appropriate event callbacks.
  var triggerApi = function(objEvents, name, callback, args) {
    if (objEvents) {
      var events = objEvents[name];
      var allEvents = objEvents.all;
      if (events && allEvents) allEvents = allEvents.slice();
      if (events) triggerEvents(events, args);
      if (allEvents) triggerEvents(allEvents, [name].concat(args));
    }
    return objEvents;
  };

  // A difficult-to-believe, but optimized internal dispatch function for
  // triggering events. Tries to keep the usual cases speedy (most internal
  // Backbone events have 3 arguments).
  var triggerEvents = function(events, args) {
    var ev, i = -1, l = events.length, a1 = args[0], a2 = args[1], a3 = args[2];
    switch (args.length) {
      case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx); return;
      case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1); return;
      case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2); return;
      case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2, a3); return;
      default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args); return;
    }
  };