What is the primary function of the findAndModify() method?

The findAndModify() method is designed to perform an atomic operation that modifies a document and then returns the updated document. This method retrieves a single document from the collection, applies the specified update operation, and returns either the original document (before the update) or the modified document (after the update) based on the parameters provided. When the option is to return the document that has just been updated, it aligns perfectly with the primary use of this method.

In typical scenarios, developers leverage findAndModify() to ensure that the document is updated and to receive the updated state right after the modification, which is crucial for many applications, especially in maintaining consistency in data handling and ensuring that further operations can be performed based on the latest document state.

This functionality makes findAndModify() particularly valuable for implementing features such as counters, preferences, or any scenario where immediate feedback about the updated state of a document is required after performing the update operation.