Hy Sy Hung Doan. Thanks for asking.

That would be another smell

Single functions are harder to unit test, to read, to reuse and to compose. They may be the first option, but once system gets serious they should be reified

Hi Maxi Contieri, Thanks for the prompt response. However, I am still on the fence. In my current project (React & Redux), we exclusively use (anonymous) functions as they are small and writing unit tests are just a breeze. I just feel like they've been convenient enough.

The code is well maintained from time to time, but no one talked about switching to use Class helpers.

I doubt if it's just a matter of preference or the scope of the projects. Mind if I ask for some more examples for the Problems you mentioned in the Code-smell-21? I'd be very glad to have a better view and understanding.