var mediator = (function(){
 
    // Storage for our topics/events
    var channels = {};
 
    // Subscribe to an event, supply a callback to be executed 
    // when that event is broadcast
    var subscribe = function(channel, fn){
        if (!channels[channel]) channels[channel] = [];
        channels[channel].push({ context: this, callback: fn });
        return this;
    };
 
    // Publish/broadcast an event to the rest of the application
    var publish = function(channel){
        if (!channels[channel]) return false;
        var args = Array.prototype.slice.call(arguments, 1);
        for (var i = 0, l = channels[channel].length; i < l; i++) {
            var subscription = channels[channel][i];
            subscription.callback.apply(subscription.context, args);
        }
        return this;
    };
 
    return {
        publish: publish,
        subscribe: subscribe,
        installTo: function(obj){
            obj.subscribe = subscribe;
            obj.publish = publish;
        }
    };
}());
 
/*** Usage ***/
(function( m ){
      // Set a default value for 'person'
      var person = "Luke";
      // Subscribe to a topic/event called 'nameChange' with
      // a callback function which will log the original
      // person's name and (if everything works) the incoming 
      // name
      m.subscribe('nameChange', function( arg ){
          console.log( person ); // Luke
          person = arg;
          console.log( person ); // David
     });
 
      // Publish the 'nameChange' topic/event with the new data
      m.publish( 'nameChange', 'David' ); 
 
})( mediator );