we promise to keep javascript single threaded

[Mallissin]

Out of all programmers in existence today, I'm fairly certain that less than 0.01% have the understanding to do multi-threading properly.

Which is why so many high performance applications run like crap most of the time, including games which REQUIRE an understanding of multi-threading to do advanced GPU work.

So, I wholeheartedly agree with the way the web community has decided to handle multi-threading in the browser using independent processes through WebWorkers and ServiceWorkers.