is there a callback option with twitter's "follow button" widget

Question

I'm using this for creating twitter follow buttons on my twitter web-app. Implementation is as easy as this:

<span id="follow-twitterapi"></span>
<script type="text/javascript">

  twttr.anywhere(function (T) {
    T('#follow-twitterapi').followButton("twitterapi");
  });

</script>

when you put that code into your html document you get this button in that span element in an iframe:

after you click follow, you get this (or a similar thing saying you're following @someone):

however i can't get any information back to my app after this button is used, (because this is rendered in an iframe and because of same-origin policy of javascript, i can't access to contents of that iframe), is there any methods provided with this widget, to inform my app when a user starts following someone using this?

Thanks.

Answer 1

You can. Here is my code:

<a href="https://twitter.com/gafitescu" class="twitter-follow-button">Follow @gafitescu</a>    
 <script src="//platform.twitter.com/widgets.js" type="text/javascript"></script>
<script type="text/javascript">
    twttr.events.bind('follow', function(event) {
        console.log(event);
        var followed_user_id = event.data.user_id;
        var followed_screen_name = event.data.screen_name;
    });
</script>