Publish and Subscribe

publish-subscribe.js

(function() {


    /**
     * Make sending and recieving messages easy.
     */
    function PubSub() {
        // Dictionary of events
        this.events = {};
    }


    /**
     * Add a subscriber
     * @param  {string}   name what do subscribe to
     * @param  {function} sub  what gets fired when triggered
     * @return {undefined}
     */
    PubSub.prototype.on = function(name, sub) {

        if (this.events[name]) {
            // Already has subscribers
            this.events[name].push(sub);
        }else{
            // No subscribers
            this.events[name] = [sub];
        }

    };


    /**
     * Remove subscriptions for an event name
     * @param  {string} name Name of event to remove subscriptions from
     * @return {undefined}
     */
    PubSub.prototype.off = function(name) {

        if (this.events[name]) {
            for (var i = 0; i < this.events[name]; i++) {

                // Null subscriptions out
                this.events[name][i] = null;
            }

            // Blow away the event
            delete this.events[name];

        }

    };


    /**
     * Publish to a subscription
     * @param  {string} name  what event gets triggered
     * @param  {value}  value what do we pass to the event
     * @return {array}        the result of each subscriber called
     */
    PubSub.prototype.trigger = function(name, value) {

        var results = [];

        // Ensure we have a subscriber for this key
        if (!this.events[name]) {
            return; // No subscribers
        }

        for (var i = 0; i < this.events[name].length; i++) {
            var subscriber = this.events[name][i];

            // Call the subscriber, passing the value
            if (typeof subscriber === "function") {
                results.push(subscriber(value));
            }

        }

        return results;

    };


    window.PubSub = new PubSub();

}());