Simple JS Pub-Sub implementation. Synchronous or Asynchronous.

pub-sub.js

/*
 * Simple Publish / subscribe events routine.
 * 
 * Used to extend an object with the subscribe and publish methods.
 * The return value of subscribe has a remove method that can be used
 * to unsubscribe.
 * 
 * Modifies the object directly.
*/
var $$ = $$ || {}; //This is the utility functions object used elsewhere.

$$.pubSub = function(el) {
    //Extend the original object or create a new empty one
    el = el || {};
  
    var topics = {};

    Object.defineProperties(el, {
        subscribe: {
            value: function(topic, listener, synchronous) {
                // Create the topic's base object if not yet created
                if(!topics.hasOwnProperty(topic)){
                    topics[topic] = [];
                }
                // Add the listener to queue
                var index = topics[topic].push({listener: listener, synchronous: !!synchronous}) - 1;

                // Provide handle back for removal of topic
                return { remove: function() {
                                    delete topics[topic][index];
                                }
                };
            }
        },

        publish: {
            value: function() {
                var args = Array.prototype.slice.call(arguments, 0),
                    topic = args.shift(); //topic is 1st arg

                // If the topic doesn't exist, or there's no listeners in queue, just leave
                if(!topics.hasOwnProperty(topic)){ 
                    return;
                };

                // Cycle through topic subscribers and call with args
                //synch or asynch alternatives
                topics[topic].forEach(function(item) {
                    if(item.synchronous){
                        item.listener.apply(null,args);
                    }else{
                        setTimeout(function(){
                            item.listener.apply(null,args);
                        }, 0);
                    }
                });
            }
        }

    });

    return el;
};

/* end */