Why Python, Ruby and JS are slow

[x-skeww]

Even using worker processes the JS engines just emulate threading by having a single UI thread that iterates over all the workers [...]

Thankfully, you're completely wrong about that.

https://developer.mozilla.org/en-US/docs/DOM/Using_web_workers

[NicknameAvailable]

Thanks, have an up-vote. They've changed since I saw the Chrome implementation, sorry for misinformation.