Firestore doesn't support JavaScript objects with custom prototypes?

Question

I'm using the node Bigquery Package, to run a simple job. Looking at the results (say data) of the job the effective_date attribute look like this:

 effective_date: BigQueryDate { value: '2015-10-02' }

which is obviously an object within the returned data object.

Importing the returned json into Firestore gives the following error:

UnhandledPromiseRejectionWarning: Error: Argument "data" is not a 
valid Document. Couldn't serialize object of type "BigQueryDate". 
Firestore doesn't support JavaScript objects with custom prototypes 
(i.e. objects that were created via the 'new' operator).

Is there an elegant way to handle this? Does one need to iterate through the results and convert / remove all Objects?

Answer 1

The firestore Node.js client do not support serialization of custom classes.

You will find more explanation in this issue:
https://github.com/googleapis/nodejs-firestore/issues/143
"We explicitly decided to not support serialization of custom classes for the Web and Node.JS client"

A solution is to convert the nested object to a plain object. For example by using lodash or JSON.stringify.

firestore.collection('collectionName')
    .doc('id')
    .set(JSON.parse(JSON.stringify(myCustomObject)));

Here is a related post:
Firestore: Add Custom Object to db

Answer 2

Another way is less resource consuming:

firestore
  .collection('collectionName')
  .doc('id')
  .set(Object.assign({}, myCustomObject));

Note: it works only for objects without nested objects.

Also you may use class-transformer and it's classToPlain() along with exposeUnsetFields option to omit undefined values.

npm install class-transformer
or
yarn add class-transformer

import {classToPlain} from 'class-transformer';

firestore
  .collection('collectionName')
  .doc('id')
  .set(instanceToPlain(myCustomObject, {exposeUnsetFields: false}));