Question 120321 in Firebase Question posted in
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How to prepare a JavaScript value for storage in Firebase Firestore?

Given an unknown JavaScript value, I would like to write it to a property of a Firestore document. But Firestore rejects some values. For example when trying to store the browser’s window object, Firestore reports an error:

#object[FirebaseError FirebaseError: [code=invalid-argument]: Function DocumentReference.update() called with invalid data.
Unsupported field value: a custom Window object (found in field data.window in document errors/Ic0sCeKezM1x1kDBI3Hy1)]

The usecase ist to write catched errors to Firestore. But catched errors can be or can contain all kinds of (nested) properties.

So how can I "prepare" an arbitrary value for storage in Firebase? Invalid values could be converted to Strings or just skipped from writing. But the coercion must always succeed.

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  1. Chosen as BEST ANSWER
    0

    Pass arbitrary objects through json-prune (https://www.npmjs.com/package/json-prune) before storing them in Firestore.


  2. 0

    While Firestore is schemaless, the list of types you can store in it is quite well defined. As you’ve found, arbitrary objects may not meet these requirements – especially not when they contain methods.

    I found it best to not accept arbitrary objects, but actually be explicit about the type of each object I store in Firestore. So for example with a TypeScript definition for each object.

    The simplest I found to coerce arbitrary JavaScript objects into Firestore compatible data is by converting them to JSON and back with:

    const firestoreData = JSON.parse(JSON.stringify(arbitraryObject));
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