code: function ( eventName ) {
          var events = this.events[ eventName ];
          if ( !events || !events.length ) {
              return null;
          }
          events = events.length === 1 ?
              [ events[ 0 ] ] :
              Array.apply( null, events );
          return function ( source, args ) {
              var i,
                  length = events.length;
              for ( i = 0; i < length; i++ ) {
                  if ( events[ i ] ) {
                      args.eventSource = source;
                      args.userData = events[ i ].userData;
                      events[ i ].handler( args );
                  }
              }
          };
      }
docs: Get a function which iterates the list of all handlers registered for a given event, calling the handler for each.
  @function
  @param {String} eventName - Name of event to get handlers for.