nodejs: verify username existence on facebook

I am trying to verify the existence of a facebook username using nodejs using the hapijs framework by sending an http request to facebook plus the username I want to search for. So "http://wwww.facebook.com/"+req.params.username And depending on the status code that is returned determine if the username is available or not. However, for facebook, a 200 status code is always returned. What do I have to do to get around this and get a 404 for a username that does not exist?