title: Firebase Realtime Database - on event - difference between Javascript Deltasnapshot and Android Java DataSnapshot
body: <p>For Firebase Realtime Database, everytime new data is added, it creates a <code>DeltaSnapshot</code> for '<code>functions</code>' and <code>DataSnapshot</code> for Android app. Documentation of the two reveal that the javascript functions based DeltaSnapshot also receives something called <code>event.Data.previous</code> which stores the prior value of the node. I can't find an equivalent in the Android documentation. Is the difference intentional? If yes, why?<br>
  Or is there a workaround/alternative way for Java that I am not able to find?</p>