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

When trying to update an array in Cloud Firestore you might run into this error: FieldValue.arrayUnion() called with invalid data. Nested arrays are not supported.

However, that error might be a bit misleading. The following code will crash:

firebase.firestore.FieldValue.arrayUnion(['javascript', 'typescript']);

You don't have a nested array per se but your code will fail because Firestore requires you to pass those items individually. All you have to do is using the spread operator instead:

firebase.firestore.FieldValue.arrayUnion(...['javascript', 'typescript']);

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Comments

[Pranav Sarda]

Really helpful post....was searching for "Adding an array into a Firebase Array Field.", with no luck. Finally, found a proper verified no for direct use of arrayUnion. Thanks a lot man.

[Bongani]

Thanks

[crowdozer]

!!

what a misleading error message, you just saved me a headache and a rewrite.

[tidianeb5]

thanks . 😊

[JanaJunkiss]

You saved my day! Thank you!

[MUGII]

thanks, it's working

[EgHubs]

You saved my day! Thank you!

[Timi]

Thank you!