js 自定义事件观察者模式(发布/订阅)

/*
 * 示例：
 * Event.create("namespace1").listen('click', function(a){
 *      console.log(a);
 * });
 * Event.create("namespace1").trigger("click", 1);
 */
window.myEvent = (function() {
   var global = this,
       Event,
       _default = 'default';

    Event = function() {
        var _listen,
            _trigger,
            _remove,
            _slice = Array.prototype.slice,
            _shift = Array.prototype.shift,
            _unshift = Array.prototype.unshift,
            namespaceCache = [],
            _create,
            find,
            each = function( ary, fn) {
                var ret;
                for(var i = 0, l = ary.length; i < l; i++) {
                    var n = ary[i];
                    ret = fn.call(n, i, n);
                }
                return ret;
            };
        // 订阅
        _listen = function(key, fn, cache) {
            if(!cache[key]) {
                cache[key] = [];
            }
            cache[key].push(fn);
        };
        // 移除订阅
        _remove = function(key, cache, fn) {
            if(cache[key]) {
                if(fn) {
                    for(var i = cache[key].length; i >=0; i++) {
                        if(cache[key][i] === fn) {
                            cache[key].splice(i, 1);
                        }
                    }
                }else {
                    cache[key] = [];
                }
            }
        };
        // 发布
        _trigger = function() {
          var cache = _shift.call(arguments),
              key = _shift.call(arguments),
              args = arguments,
              _self = this,
              ret,
              stack = cache[key];
            if(!stack || !stack.length) {
                return;
            }
            return each(stack, function() {
               return this.apply(_self, args);
            });
        };
        // 创建命名空间
        _create = function(namespace) {
            var namespace = namespace || _default;
            var cache = {},
                offlineStack = [],  // 离线事件
                ret = {
                    listen: function (key, fn, last) {
                        _listen(key, fn, cache);
                        if (offlineStack == null) {
                            return;
                        }
                        if (last === 'last') {
                            offlineStack.length && offlineStack.pop()();
                        } else {
                            each(offlineStack, function () {
                                this();
                            });
                        }
                        offlineStack = null;
                    },

                    one: function (key, fn, last) {
                        _remove(key, cache);
                        this.listen(key, fn, last);
                    },

                    remove: function(key, fn, last) {
                        _remove(key, cache, fn);
                    },

                    trigger: function() {
                        var fn,
                            args,
                            _self = this;
                        _unshift.call(arguments, cache);
                        args = arguments;
                        fn = function() {
                            return _trigger.apply(_self, args);
                        };
                        if(offlineStack) {
                            return offlineStack.push(fn);
                        }
                        return fn();
                    }
                };

                return namespace ? (namespaceCache[namespace] ? namespaceCache[namespace] : namespaceCache[namespace] = ret) : ret;
            };

        return {
            create: _create,
            one: function(key, fn, last) {
                var event = this.create();
                event.one(key, fn, last);
            },
            remove: function(key, fn) {
                var event = this.create();
                event.remove(key, fn);
            },
            listen: function(key, fn, last) {
                var event = this.create();
                event.listen(key, fn, last);
            },
            trigger: function() {
                var event = this.create();
                event.trigger.apply(this, arguments);
            }
        };
    }();
    return Event;
})();