insertOne modifies input query object

[Big_Cat_Public_Safety_Act (Why would a 300 kg wild predator be satisfied living inside a cage?)]

userInfo = {
      name: 'Magical Mr. Mistoffelees',
      email: 'magicz@cats.com',
      password: 'somehashedpw'
}

await users.insertOne(userInfo, {
  writeConcern: { w: "majority", wtimeout: 100 },
})

console.log(userInfo)

{
      name: 'Magical Mr. Mistoffelees',
      email: 'magicz@cats.com',
      password: 'somehashedpw',
      _id: 6279884c2b402a8f82efa162
}

Is this expected behavior? It added an _id field.

[SourabhBagrecha]

Hi @Big_Cat_Public_Safety_Act,

@Big_Cat_Public_Safety_Act

Is this expected behavior? It added an _id field.

Yes, it is the expected behavior. MongoDB automatically adds an _id field so as to uniquely identify each and every document in the collection.

In case you have any doubts, please feel free to reach out to us.

Thanks and Regards.
Sourabh Bagrecha,
MongoDB