Firebase database. How to append values to array?

Question

I have the following test data

1: {
 
  match: "Game 1",
  scorer: ["foo","bar"] //this could also be an object
}

My question is how do I correctly append new value to an array without overwriting it? My idea was to retrieve existing data then spread it like so [...currentData, "bob"]. Is there a better alternative?

const addScorer = (matchId) => {
 return update(ref(db, path), {
  scorer: ["bob"]
 })
}

[firebase.google.com/docs/database/web/… hey look in to this it will solve your issue — Nilesh Mishra
– Nilesh Mishra, Commented Feb 20, 2022 at 15:36

Frank van Puffelen · Accepted Answer · 2022-02-20 15:43:31Z

1

There is no atomic operation to add an item to an array directly in the database. This means you'll need to:

Read the array into your application code
Append the item to the array
Write the entire array back to the database

This is one of the many reasons why Firebase recommends against using arrays for lists of data, but instead has a push() operation that circumvents most problems. For more on this, see the link to the document that Nilesh included in their comment, or read this article on Best Practices: Arrays in Firebase.

answered Feb 20, 2022 at 15:43

Frank van Puffelen

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2 Comments

Steve Over a year ago

This is no longer true. There is a FieldValue.arrayUnion and arrayRemove.

Frank van Puffelen Over a year ago

The question is about the Realtime Database, while FieldValue.arrayUnion and arrayRemove are only available for Cloud Firestore.

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