How to remove multiple elements from a Firestore Array dynamically?

Question

I want to remove multiple elements from my Firestore array:

var eliminatedThisRound = []

for (const player in players){
    if (players[player].eliminated === false && players[player].answer !== answer) {
        eliminatedThisRound.push(players[player].uid);
    }
}
var update = {
    roundFinished: true,
    nextRound: date.valueOf() + 12000,seconds
    players: updatedPlayers,
    remainingPlayers: admin.firestore.FieldValue.arrayRemove(eliminatedThisRound)
}
await t.update(gameRef, update);

The above returns this error:

transaction failure: Error: Element at index 0 is not a valid array element. Nested arrays are not supported.

So it would be fine if I knew the values, as I could do something like this:

remainingPlayers: admin.firestore.FieldValue.arrayRemove("player1", "player2")

However I haven't found a way to make the parameter of arrayRemove() dynamic.

Any idea?

As far as I can see you should be able to pass in multiple values for arrayRemove: firebase.google.com/docs/reference/js/… and firebase.google.com/docs/reference/js/…. What happens when you pass multiple values? Is there an error message? — Frank van Puffelen
– Frank van Puffelen, Commented Jan 3, 2021 at 7:21
Yes that's right - but my values are dynamic. I tried to pass in an array which had multiple values in it (eliminatedThisRound in my code above) - however it returned this error: Element at index 0 is not a valid array element. Nested arrays are not supported. — Zorgan
– Zorgan, Commented Jan 3, 2021 at 8:05
Ah, that error message makes sense (please include that right away in the future). The spread operator in Renaud's answer should make that error disappear. — Frank van Puffelen
– Frank van Puffelen, Commented Jan 3, 2021 at 16:31

Renaud Tarnec · Accepted Answer · 2021-01-03 12:00:12Z

7

You need to use the Spread operator, as follows, in order to pass all elements of eliminatedThisRound as arguments to the arrayRemove() method.

var eliminatedThisRound = []

for (const player in players){
    if (players[player].eliminated === false && players[player].answer !== answer) {
        eliminatedThisRound.push(players[player].uid);
    }
}
var update = {

    // ...

    admin.firestore.FieldValue.arrayRemove(...eliminatedThisRound)
}

await t.update(gameRef, update);

Note that you should have at least one element in the Array, otherwise you will call arrayRemove() with 0 argument while it requires at least 1 argument. So you may check the array length before assigning the remainingPlayers property to the update Object.

edited Jan 3, 2021 at 12:00

answered Jan 3, 2021 at 11:31

Renaud Tarnec

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Comments

dshukertjr · Accepted Answer · 2021-01-03 08:04:18Z

1

You can pass a single value or an array of values from variables like this to arrayRemove():

var removingPlayersId = ['player1', 'player2'];
  admin
    .firestore()
    .doc('game/someID')
    .set(
      {
        remainingPlayers: admin.firestore.FieldValue.arrayRemove(
          removingPlayersId
        ),
      },
      { merge: true }
    );

answered Jan 3, 2021 at 8:04

dshukertjr

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