Comment Re:yes but does it... (Score 1) 60
If you checked out the demos, such as bananabread, emscripten is fully capable of doing javascript threading.
That is, any work that does not need DOM access can be done on background threads.
The "freezing" and "time slicing" are not particularly interesting objections. Any application that has to interact with the DOM has the same issue, which is why JavaScript hasn't solved it on the main thread, apart from the perfectly reasonable approach of event based code. And yes, this means using setTimeout and requestAnimationFrame on the main thread. Big deal.
The objection to highlevel language? Really not interesting. Might as well apply that to perl, python, ruby even java has a runtime JIT for its bytecode, and while I don't know much about "portable" NaCL, I imagine it does too.
JavaScript JITs are not a significant portion of the program's overhead. You may be able to do better in NaCL but at the loss of browser support, cross-platform support, integration into the whole universe of existing JavaScript, extensibility by other scripts/addons and even readability (yes, I've read through emscripten generated code when debugging. not high on readability, but certainly higher than assembly).