events.js

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

// A module that can be mixed in to *any object* in order to provide it with
// custom events. You may bind with `on` or remove with `off` callback
// functions to an event; `trigger`-ing an event fires all callbacks in
// succession.
//
//     var object = {};
//     _.extend(object, Backbone.Events);
//     object.on('expand', function(){ alert('expanded'); });
//     object.trigger('expand');
//
(function(){
    // Create local references to array methods we'll want to use later.
    var array = [];
    var push = array.push;
    var slice = array.slice;
    var splice = array.splice;

    var Events = {

        // Bind an event to a `callback` function. Passing `"all"` will bind
        // the callback to all events fired.
        on: function(name, callback, context) {
            if (!eventsApi(this, 'on', name, [callback, context]) || !callback) return this;
            this._events || (this._events = {});
            var events = this._events[name] || (this._events[name] = []);
            events.push({callback: callback, context: context, ctx: context || this});
            return this;
        },

        // Bind an event to only be triggered a single time. After the first time
        // the callback is invoked, it will be removed.
        once: function(name, callback, context) {
            if (!eventsApi(this, 'once', name, [callback, context]) || !callback) return this;
            var self = this;
            var once = _.once(function() {
                self.off(name, once);
                callback.apply(this, arguments);
            });
            once._callback = callback;
            return this.on(name, once, context);
        },

        // 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.
        off: function(name, callback, context) {
            var retain, ev, events, names, i, l, j, k;
            if (!this._events || !eventsApi(this, 'off', name, [callback, context])) return this;
            if (!name && !callback && !context) {
                this._events = {};
                return this;
            }

            names = name ? [name] : _.keys(this._events);
            for (i = 0, l = names.length; i < l; i++) {
                name = names[i];
                if (events = this._events[name]) {
                    this._events[name] = retain = [];
                    if (callback || context) {
                        for (j = 0, k = events.length; j < k; j++) {
                            ev = events[j];
                            if ((callback && callback !== ev.callback && callback !== ev.callback._callback) ||
                                (context && context !== ev.context)) {
                                retain.push(ev);
                          }
                        }
                    }
                    if (!retain.length) delete this._events[name];
                }
            }

            return this;
        },

        // 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).
        trigger: function(name) {
            if (!this._events) return this;
            var args = slice.call(arguments, 1);
            if (!eventsApi(this, 'trigger', name, args)) return this;
            var events = this._events[name];
            var allEvents = this._events.all;
            if (events) triggerEvents(events, args);
            if (allEvents) triggerEvents(allEvents, arguments);
            return this;
        },

        // Tell this object to stop listening to either specific events ... or
        // to every object it's currently listening to.
        stopListening: function(obj, name, callback) {
            var listeners = this._listeners;
            if (!listeners) return this;
            var deleteListener = !name && !callback;
            if (typeof name === 'object') callback = this;
            if (obj) (listeners = {})[obj._listenerId] = obj;
            for (var id in listeners) {
                listeners[id].off(name, callback, this);
                if (deleteListener) delete this._listeners[id];
            }
            return this;
        }
    };

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

    // Implement fancy features of the Events API such as multiple event
    // names `"change blur"` and jQuery-style event maps `{change: action}`
    // in terms of the existing API.
    var eventsApi = function(obj, action, name, rest) {
        if (!name) return true;

        // Handle event maps.
        if (typeof name === 'object') {
            for (var key in name) {
                obj[action].apply(obj, [key, name[key]].concat(rest));
            }
            return false;
        }

        // Handle space separated event names.
        if (eventSplitter.test(name)) {
            var names = name.split(eventSplitter);
            for (var i = 0, l = names.length; i < l; i++) {
                obj[action].apply(obj, [names[i]].concat(rest));
            }
            return false;
        }

        return true;
    };

    // 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);
        }
    };

    var listenMethods = {listenTo: 'on', listenToOnce: 'once'};

    // Inversion-of-control versions of `on` and `once`. Tell *this* object to
    // listen to an event in another object ... keeping track of what it's
    // listening to.
    _.each(listenMethods, function(implementation, method) {
        Events[method] = function(obj, name, callback) {
            var listeners = this._listeners || (this._listeners = {});
            var id = obj._listenerId || (obj._listenerId = _.uniqueId('l'));
            listeners[id] = obj;
            if (typeof name === 'object') callback = this;
            obj[implementation](name, callback, this);
            return this;
        };
    });

    // Aliases for backwards compatibility.
    Events.bind   = Events.on;
    Events.unbind = Events.off;

    if(typeof define === 'function' && define['amd']){
        define(['underscore'], function(){
            return Events;
        });
    }
    else{
        window.Events = Events;
    }
})();