js 发布订阅

var Event = (function() {
    var clientList = {};
    var listen,
        trigger,
        remove;
    listen = function(key, fn) {
        if (!clientList[key]) {
            clientList[key] = [];
        }
        clientList[key].push(fn);
    };

    trigger = function() {
        var key = [].shift.call(arguments);
        var fns = clientList[key];

        if (!fns || fns.length === 0) {
            return false;
        }

        for (var i = 0, fn; fn = fns[i++];) {
            fn.apply(this, arguments);
        }
    };


    remove = function(key, fn) {
        var fns = clientList[key];

        // key对应的消息么有被人订阅
        if (!fns) {
            return false;
        }

        // 没有传入fn(具体的回调函数), 表示取消key对应的所有订阅
        if (!fn) {
            fns && (fns.length = 0);
        }
        else {
            // 反向遍历
            for (var i = fns.length - 1; i >= 0; i--) {
                var _fn = fns[i];
                if (_fn === fn) {
                    // 删除订阅回调函数
                    fns.splice(i, 1);
                }
            }
        }
    };

    return {
        listen: listen,
        trigger: trigger,
        remove: remove
    }
}());