Parsing the response object from sending a Facebook Invite Friend Request

I am working with the Facebook Javascript SDK and I am trying to set up a rewards system for sending invites to Friends. Basically, I want to give the user points for simply sending invites to their friends using the friend invite dialog provided by the Facebook Javascript SDK. That said, I set everything up based on the Friend Smash tutorial on the FB developers website and I am creating a custom, multi-friend selector to send invites. The invite dialog comes up properly and the invite sends correctly.

The Javascript that sends the invite looks like this:

function sendRequest() {
               // Get the list of selected friends
               var sendUIDs = '';
               var mfsForm = document.getElementById('mfsForm');
                 for(var i = 0; i < mfsForm.friends.length; i++) {
                   if(mfsForm.friends[i].checked) {
                     sendUIDs += mfsForm.friends[i].value + ',';
                   }
                 }

               // Use FB.ui to send the Request(s)
               FB.ui({method: 'apprequests',
                 to: sendUIDs,
                 title: 'Help me get some points!',
                 message: 'Help me get some points by coming over to XXX and registering to play!',
               }, callback);
             }

However the request's response object looks like this when sending to one friend:

{request: "412752342228182", to: Array[1]}

And it looks like this when inviting two friends:

{request: "414967121961627", to: Array[2]}

The object contains the "request" field which is the unique request ID for the invite, as expected. The Facebook documentation states I am supposed to get an array of user IDs of the recipients in the response object's "to" field but that strange Array[X] is there instead. Is this the correct response? Am I missing something?

Any help on this is appreciated. Thanks in advance for your time.