How do I add an object to an array in Firestore?

Question

I'm trying:

await firebase.firestore().doc(`documents/${documentData.id}`).update({
    predictionHistory: firebase.firestore.FieldValue.arrayUnion(...[predictions])
});

where predictions is an array of:

export interface PredictionHistory {
    predictedAt: firebase.firestore.Timestamp;
    predictionText: string;
}

But I get an error:

FirebaseError: Function FieldValue.arrayUnion() called with invalid data. Nested arrays are not supported

Any idea what I'm doing wrong?

Hey Shamoon. Did you get anywhere with this? I tried helping with an answer below. Did you have a chance to check that out and try it? — Frank van Puffelen
– Frank van Puffelen, Commented Jun 17, 2021 at 4:01

Frank van Puffelen · Accepted Answer · 2021-06-07 21:30:51Z

1

I think you may be overcomplicating the call, and be looking for:

predictionHistory: firebase.firestore.FieldValue.arrayUnion(predictions)

This will add any elements from the predictions array that are not yet in the predictionHistory field.

answered Jun 7, 2021 at 21:30

Frank van Puffelen

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