How to change / add a class to a functional component in react?

Question

React

In general, I would like to know how to solve this issue. Here I mean style classes. Particularly interesting when using modularity in css
The topic is interesting precisely from the point of view of the functional component

Answer 1

If I understood the question correctly, then:
https://github.com/JedWatson/classnames
"A simple javascript utility for conditionally joining classNames together"