For this use case, I suspect you wouldn't be able to win much with WebWorkers. You'd have to profile, but having done a lot of profiling with multithreading in several environments I've learned to expect disappointment relative to my initial lofty hopes. It feels like it ought to be easy to get linear speedups and that it ought to take something really unusual and special to slow it down; in practice you're lucky to even get "good" speedups.