Is it possible to somehow store the value of a variable on the client?

Question

JavaScript

I sat down to write an application in react native and, after thinking a couple of steps forward, I realized that each user would need to store their own values ​​​​of some variables for each user. Example: applications with exercises where there is a choice of difficulty, where the user selects the number of seconds that the exercise will go. If I understand correctly, then these values ​​​​are stored on the user's phone, and not in a database somewhere on the server.
Actually the question is how to change it for each specific user? How is this done in js(react) and how, for example, in Java?

Answer 1

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