[bslatkin]

Scala has a lot of interesting concepts in it for sure! The problem is that the JVM is a deal-breaker, either because of its complexity or because of the associated licensing risk. Clojure has the same problem, for what it's worth.

[Lerc]

I think intrinsic to that deal-breaker is the underlying problem. Memory management in a parallel environment is a tough nut to crack. Leaning on the JVM punts on the issue.

There's no reason JavaScript couldn't transparently implement parallel map/filter/etc. Other than the fact it is really hard to do. On the other hand a lot of the things JavaScript engines do today are also really hard, so maybe one day it'll happen.