javascript的事件触发和接收源码

define(function(require,exports,module){
 
    var Events=function(){
        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);
            }
        };
 
        // Aliases for backwards compatibility.
        Events.bind   = Events.on;
        Events.unbind = Events.off;
        return Events;
    }()
 
module.exports=Events
 
})