title: Angular2+ filter firebase data
body: <p>I want to filter some data from the <code>FirebaseListObservable</code> but I don't know how to perform it. For the normal case <a href="https://plnkr.co/edit/RQOk2EYS6TcYX52JTO69?p=preview" rel="nofollow noreferrer">here</a> is the solution but using the real time database it doesn't work. Please help.</p>