useSelector

[lishine]

Observer uses useSelector as well. So where is the performance gain coming from? Is it from using one useSelector per component instead of multiple ?

[jmeistrich]

Yes, exactly. In our benchmarks we find the performance cost of observer to be the same as the cost of useSelector, which suggests there’s little to no overhead beyond its use of useSelector. And then each additional use of useSelector (or any hook) adds extra overhead. But observer wraps it all into one hook call, so it has a fixed cost of one hook.