Child_added get last item added javascript

Question

For my Firebase cloud functions, i'am trying to get the last child item added, in the aim to proceed a task for this item. My structure is like this:

  -Tips
      -TipsId
             -Safe
                  -SafeId
                  -SafeId
                   etc

My goal is to get the last child SafeId item added. i found this snippet, but the problem is that it is also trigger when item SafeId is remove.

ref.orderByChild('timestamp').startAt(Date.now()).on('child_added',function(snapshot) {
  console.log('new record', snapshot.val());
});

Answer 1

To get just the last item, just limitToLast() :

ref.orderByChild('timestamp').limitToLast(1).on('child_added',function(snapshot) {
  console.log('new record', snapshot.val());
});

If you don't have a timestamp property, but have used push() to add the items, you can also use orderByKey() :

ref.orderByKey().limitToLast(1).on('child_added',function(snapshot) {
  console.log('new record', snapshot.val());
});