[dceddia]

Oh hey, that's me! :wave:

I definitely agree useEffect is awfully cryptic and easy to get wrong, and I'm happy to be corrected... but I'm not sure how I'm wrong about it running on every render when there's no 2nd argument?

I kinda wish they'd made it easier to do the common operations like onMount and onUnmount by providing some simplified wrappers around useEffect (with less power comes less responsibility... or something). Of course we can make custom hooks for those, but having the well-trodden paths be paved is always nice.

[pcthrowaway]

I misunderstood what you were saying about it running on unmount when the dependency array is empty.

Of course, it does run on unmount when the dependency array is empty, and it runs on unmount when there are dependencies in the dependency array.

But upon re-reading what you said, I think your intent was that it's comparable to componentWillUnmount() in class-based React only when the dependency array is empty (because otherwise the cleanup function also gets called when dependencies change).

My apologies, as I never really used class-based React, so the distinction was lost on me (and also forgot about the cleanup function being called between useEffect callback calls)

[dceddia]

Oh gotcha, no worries. I'm not sure if you meant to reply to me anyway, my comment was in regards to knodi123's original comment that linked to an article of mine and said it was wrong about when useEffect re-renders – but the comment was edited and that part is gone, so now mine looks entirely crazy haha.

[knodi123]

I edited it because I realized I was wrong - I was confused by the difference between no 2nd argument, and [] for the 2nd argument. But again - as a full time professional web developer, who has being using React for a few years, I think that also goes towards my point. ;-)

[dceddia]

Hahah, yeah, this whole set of threads just hammers home your point, really :D