I’m from the same world as you and here’s how I understood this:

Any function that’s not pure should be a ~class~ component.

ie, when you have a bunch of functions that operate on the same kind of struct/set of state, and in fact you want to prevent other functions from messing with it (you want to make it internal), you group them in some way. The OO word for that is a class. React is a component; which are much more composable because we ditched the stricter concept of inheritance of OO classes.

Hell, the es6 class system is really just syntactic sugar around Brendan Eich’s nifty prototypal system. If it weren’t for the weak typing and lack of std.lib, JavaScript would be an amazing language.

…which is to say it would probably be Go haha