CODEWITHSUNDEEP
javascriptfirebasefirebase-realtime-database
shures
shures

Reputation: 43

how to get second last value from firebase database in web javascript?

Here is my code that retrieves last value 

Firebase
  .database()
  .ref('comment/commentHistory/' + postId)
  .limitToLast(1)
  .once('value', (snapshot) => {
    // Stuff                
  });

Upvotes: 3

Views: 1694

Answers (1)

Jeremy
Jeremy

Reputation: 3738

Are your postIds sequential? If they are, you can use the orderByKey clause. If they're not, you'll need to add some kind of counter or timestamp.

Firebase
  .database()
  .ref('comment/commentHistory')
  .orderByKey
  .limitToLast(2)
  .once('value', (snapshot) => {
      // take the last item with the lowest key in the snapshot
  });

If your data isn't sequential, you'll need to add a timestamp as a child to your post.

Then you could use the orderByChild clause:

 Firebase
      .database()
      .ref('comment/commentHistory')
      .orderByChild('timestamp')
      .limitToLast(2)
      .once('value', (snapshot) => {
          // take the last item with the lowest timestamp in the snapshot
      });

Upvotes: 1

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