It's not blazingly fast, no, but it's not as much overhead as people think either when they're imagining what it would cost to do the same thing with malloc. TC39 knew all this when they picked { step, done } as the API for iteration and they still picked it, so I'm not really introducing new risk but rather trusting that they knew what they were doing when they designed string iterators.

At the moment the consensus seems to be that these language features haven't been worth investing much in optimizing because they aren't widely used in perf-critical pathways. So there's a chicken and egg problem, but one that gives me some hope that these APIs will actually get faster as their usage becomes more common and important, which it should if we adopt one of these proposed solutions to the current DevX problems