原生 JS 实现全局发布订阅事件

var Event = (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;
            };

        _listen = function(key, fn, cache) {
            if (!cache[key]) {
                cache[key] = []
            }
            cache[key].push(fn)
        };
        _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] = []
            }
        };
        _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);
            });
        };
        _create = function(namespace) {
            var namespace = namespace || _default;
            var cache = {},
                offineStack = [], //离线事件
                ret = {
                    listen: function(key, fn, last) {
                        _listen(key, fn, cache);
                        if (offineStack === null) {
                            return;
                        }
                        if (last === 'last') {
                            offineStack.length && offineStack.pop();
                        } else {
                            each(offineStack, function() {
                                this()
                            });
                        }
                        offineStack = null
                    },
                    one: function(key, fn, last) {
                        _remove(key, cache);
                        this.listen(key, fn, last)
                    },
                    remove: function(key, fn) {
                        _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 (offineStack) {
                            return offineStack.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
})();