Simple PubSub snippet for both browser and nodejs (just remove outer wrap-function).

example-jquery.js

/* Use PubSub on e.g. jQuery */
PubSub.apply($);

function addText(text) {
  $('body').append('<p>' + text + '</p>');
}
function logChange(text) {
  console.log('new text: ' + text);
}

/* Subscribe */
$.subscribe('textInput', addText);
$.subscribe('textInput', logChange);

/* Publish */
$('form').submit(function () {
  var text = $('input[name=text]').val();
  $.publish('textInput', [text]);
});

/* Unsubscribe */
$.unsubscribe('textInput', logChange);

example.js

var pubsub = new PubSub();

/* Subscribe */
pubsub.subscribe('topic', fn);

/* Publish */
pubsub.publish('topic', [arg1, arg2, ..., argN]);

/* Unsubscribe */
pubsub.unsubscribe('topic', fn);

pubsub.js

// pretty - 582 bytes (260 bytes gzipped)

(function (exports) {
    "use strict";

    exports.PubSub = function () {
        var index = {};

        this.publish = function (topic, exposure) {
            var subscribers = index[topic],
                i = subscribers.length;
            while (--i + 1) {
                subscribers[i].apply(this, exposure || []);
            }
        };
        this.subscribe = function (topic, subscriber) {
            (index[topic] = index[topic] || []).push(subscriber);
        };
        this.unsubscribe = function (topic, subscriber) {
            var subscribers = index[topic],
                i = subscribers.length;
            while (--i + 1) {
                if (subscribers[i] === subscriber) {
                    subscribers.splice(i, 1);
                }
            }
        };
    };
}(window));



// minified - 280 bytes (178 bytes gzipped)

(function(f){f.PubSub=function(){var e={};this.publish=function(a,d){for(var b=e[a],c=b.length;--c+1;)b[c].apply(this,d||[])};this.subscribe=function(a,d){(e[a]=e[a]||[]).push(d)};this.unsubscribe=function(a,d){for(var b=e[a],c=b.length;--c+1;)b[c]===d&&b.splice(c,1)}}})(window);