mediator.js

 /* 
  * I needed it 'cause I have a generic js to add embeded subForms to a Form
  * appending the prototype upon AddButton JQuery click event. So to add event 
  * bindings to one of the controls generated out of the prototype template, which
  * is unknown to the js that adds it, I fire a message like "prototype_just_added"
  * and the specific js catches it and binds the event.
  */

/* 
 * MediatorPatter implementaton to allow for some behavior extensions.
 * 
 * 
 * Example use:
 * <code>
 * m = new docdigital.Mediator(); // Central Mediator Object.
 * a = new docdigital.Subscriber('name', function(message, from) {alert(message)}); // `a` is a handler
 * m.register(a, 'allowAddFields.crearNuevo'); // `a` listens for 'allowAddFields.crearNuevo' message and alerts it
 * m.send('allowAddFields.crearNuevo'); // Mediator notifies a, sender is undefined (i.e. anonymous).
 * 
 * // pair [message, subscriber.name] must be unique.
 * b = new docdigital.Subscriber('name2', function(message, from) {alert(message)});
 * c = new docdigital.Subscriber('name3', function(message, from) {alert(message)});
 * m.register(b, 'allowAddFields.crearNuevo'); // `a` listens for 'allowAddFields.crearNuevo' message and alerts it
 * m.send('allowAddFields.crearNuevo', b); // Mediator notifies only (`a` and `c`) as `b` is sender.
 * m.send('allowAddFields.crearNuevo', b, a); // Mediator notifies only `a` as b is sending to a.
 * m.send('allowAddFields.crearNuevo', a, a); // Mediator notifies only `a` message from `a`.
 * // Only listeners MUST be registered, sender could be any object, or none.
 * </code>
 * 
 * Inspired in {@link http://www.dofactory.com/javascript-mediator-pattern.aspx} chat sample code
 * added the possibility to notify only the listeners registered to the sending message.
 */
var docdigital = docdigital || {};
$.extend(true, docdigital, {
    constants: {
        mediator: {
            messages: {}
        }
    },
    mediatorInstance: null,
    Subscriber: function(name, receive) {
        this.name = name;
        this.Mediator = null;
        this.receive = receive || this.receive;
    },
    Mediator: function() {
        var subscribers = {};
        return {
            register: function(subscriber, message) {
                message = message || 'empty';
                subscribers[message] = subscribers[message] || {};
                subscribers[message][subscriber.name] = subscriber;
                subscriber.Mediator = this;
            },
            send: function(message, from, to) {
                if (to) {                      // single message
                    to.receive(message, from);    
                } else {                       // broadcast message to message's subscribers
                    for (key in subscribers[message]) {   
                        if (subscribers[message][key] !== from) {
                            if (false === subscribers[message][key].receive(message, from)) {
                                break;
                            }
                        }
                    }
                }
            }
        };
    }
});

docdigital.Subscriber.prototype = {
    send: function(message, to) {
        this.Mediator.send(message, this, to);
    },
    receive: function(message, from) {}
};

docdigital.mediatorInstance = new docdigital.Mediator();

/**
 * Example usage follows
 */

/**
 * Adding message in the sender file (in my case the js adding prototype subForms), 
 * this doesn't need to be a constant, you could spread repeated literal strings too..
 * And sending the message when appropriate.
 */
var docdigital = docdigital || {};
$.extend(true, docdigital, {
    constants: {
        mediator: {
            messages: {
                clonePrototype_prototypeAdded: 'clonePrototype_prototypeAdded'
            }
        }
    },
    ColonePrototype: function () {
            // ... generic code to append prototype templates
            $clone = $.parseHTML($clone);
            $(this).append($clone);
            docdigital.mediatorInstance.send(
                docdigital.constants.mediator.messages.clonePrototype_prototypeAdded,
                $clone
            );
        }
});

/**
 * registering a listener/handler somewhere else.
 */
 // subscriber is binded to a callback fn
 var subscriber = new docdigital.Subscriber('buttonAdd', docdigital.Listeners.documentType.fieldTypeChangeEvent); 
 // register subscriber to a message. docdigital.constants.mediator.messages.clonePrototype_prototypeAdded
 docdigital.mediatorInstance.register(
     subscriber, docdigital.constants.mediator.messages.clonePrototype_prototypeAdded
 );