Should I use an ORM for guest mode? temporary/persistent data

I am currently developing a single page JS app. It will pull in/store data from a REST API.

My plan was that the user would register, then login, When they change the data it updates their info in the db. when they later login, the app would populate the interface with their data from the database via the api and also allow it to be updated.

However I have now decided that I would like a guest mode. So that initially when the app loads the user can fully use the app, set data, update data. see the results. But not need to register. If they then register it stores what they have done. Associates the work with the created user account so that they can login and have it load as usual.

I am now trying to decide how this would be done. Should I use an ORM?, that way both guest and registered would run through the same interface except the registered would persist?

Any suggestions would be welcome

via Elbolton