简化版的 js 订阅者模式实现代码，简化了 [PubSub](https://github.com/mroderick/PubSubJS)

PubSub.js

var PubSub = (function() {
    var messages = {},
        lastUid = -1;

    function hasKeys(obj) {
        for (var key in obj){
            return true;
        }
        return false;
    }

    return {
        /**
         * Publishes the message, passing the data to it's subscribers
         * @param { String } message The message to publish
         * @param {} data The data to pass to subscribers
         *  */ 
        publish: function(message, data) {
            if (!message) return false;
            var topic = message ? message.toString() : '';
            var hasSubscribers = messages.hasOwnProperty( topic ) && hasKeys(messages[topic]);
            if (!hasSubscribers) {
                return false;
            }
            var subscribers = messages[topic];
            for (var i in subscribers) {
                setTimeout( subscribers[i](data), 0 );
            }
        },
        /**
         * Subscribes the passed function to the passed message. Every returned token is unique and should be stored if you need to unsubscribe
         * @function
         * @param { String } message The message to subscribe to
         * @param { Function } func The function to call when a new message is published
         * @return { String }
         */
        subscribe: function(message, func) {
            if (!message) return false;
            var topic = message ? message.toString() : '';

            if ( typeof func !== 'function'){
                return false;
            }

            // topic is not registered yet
            if ( !messages.hasOwnProperty( topic ) ){
                messages[topic] = {};
            }
            var token = 'uid_' + String(++lastUid);
            messages[topic][token] = func;
            // return token for unsubscribing
            return token;
        },
        /**
         * Removes subscriptions
         *
         * - When passed a token, removes a specific subscription.
         *
         * - When passed a topic, removes all subscriptions for that topic (hierarchy)
         * @function
         * @public
         * @param { String } value A token or topic to unsubscribe from
         * @example // Unsubscribing with a token
         * var token = PubSub.subscribe('mytopic', myFunc);
         * PubSub.unsubscribe(token);
         * @example // Unsubscribing from a topic
         * PubSub.unsubscribe('mytopic');
         */
        unsubscribe: function(value){
            var isTopic = messages.hasOwnProperty(value);
            if (isTopic) {
                delete messages[value];
            } else { // is Token
                for (var m in messages){
                    if (messages[m].hasOwnProperty(value)){
                        delete messages[m][value];
                        // tokens are unique, so we can just stop here
                        break;
                    }
                }
            }
        }
    }
})();