Yeah, it most likely is not. I mix imperative, OOP, and functional all the time. Parts of my codebase that has to do with algorithms are written using imperative style, the "public API" is OOP (class, object, methods) which makes the use of my library a breeze, and the rest is functional.

To give you an example of how you would use some crypto-related library that implemented its API (?) in OOP:

  let x = new Foo.bar in
  x#absorb a;
  x#squeeze b;
  x#reset

Or take a look at: https://github.com/xavierleroy/cryptokit/blob/master/src/cry...

This (this entire file) is a great example, too!