Firebase child_added only get child added

Question

From the Firebase API:

Child Added: This event will be triggered once for each initial child at this location, and it will be triggered again every time a new child is added.

Some code:

listRef.on('child_added', function(childSnapshot, prevChildName) {     // do something with the child }); 

But since the function is called once for each child at this location, is there any way to get only the child that was actually added?

Answer 1

To track things added since some checkpoint without fetching previous records, you can use endAt() and limit() to grab the last record:

// retrieve the last record from `ref` ref.endAt().limitToLast(1).on('child_added', function(snapshot) {     // all records after the last continue to invoke this function    console.log(snapshot.name(), snapshot.val());  }); 

Answer 2

limit() method is deprecated. limitToLast() and limitToFirst() methods replace it.

// retrieve the last record from `ref` ref.limitToLast(1).on('child_added', function(snapshot) {     // all records after the last continue to invoke this function    console.log(snapshot.name(), snapshot.val());    // get the last inserted key    console.log(snapshot.key());  });