const firebase = require('firebase')

// Please use your firebase config here
firebase.initializeApp(firebaseConfig)

const document = {
  someArray: [
    { text: '' },
  ],
}

const converter = {
  toFirestore: (modelObject) => {
    console.log('toFirestore', modelObject)
    modelObject.someArray = 'text'
    return { text: modelObject.someArray[0].text }
  },
  fromFirestore: () => {
    throw new ReferenceError()
  },
}

// log 'toFirestore' twice, and then fail second conversion.
firebase.firestore().collection('posts')
  .withConverter(converter)
  .add(document)

// log 'toFirestore' only once and complete as expected.
firebase.firestore().collection('posts')
  .withConverter(converter)
  .doc()
  .set(document)