The other advantage of the filter one is it can be stuck in the middle of a bunch of other list operations - map(), sort(), slice(), other filters(). Also, you can use findIndex() instead of indexOf() to match any arbitrary predicate, instead of exact equivalence.

Oh, for sure. I know .filter() has it's place, so if you need anything beyond making the array unique, I'd definitely use your solution.

The one I posted just blew my mind a little the first time I saw it, so I love to share it. I guess I never really considered spreading a set.