WP3.5 Media Uploader – how to make it accept multiple images?

I’m wondering how to make WP3.5 media uploader return 2 or more items in attachement? It always runs once even if 2 items are selected. The code:

$('.button').on('click', function(){
     var send_attachment_backup = wp.media.editor.send.attachment;
          wp.media.editor.send.attachment = function(props, attachment){                                
               myFunction(attachment.url);
          wp.media.editor.send.attachment = send_attachment_backup;
     }
     wp.media.editor.open();
});

EDIT: My mistake. I’m doing wp.media.editor.send.attachment = send_attachment_backup; and it runs once. So the new questions would be: how to restore the original function after the latest item in the loop?