You don't need tail calls in JavaScript in order have them in a language that compiles to JS. The tail call can be compiled as a while loop. This is what Scala does on the JVM (and presumably what Scala.js does as well).

This only works with calls that can be resolved at compile time (unless you mean a trampoline). That happens to be most of the common use, which is great, but it's not perfect.

Trampolines still work, albeit with a pretty substantial perf penalty.

No. Automatic tail call elimination can't be implemented without breaking JS semantics.

Manual tail calls can perfectly well be implemented without breaking anything.

Of course! The parent mentioned JS getting them however, which is, as I mentioned, impossible.

Yeah, just add goto!

Yes, add goto. If JS is going to be the "assembly language of the web", it needs a general branch construct or it will suck.

Well then I dream of a day when an ecmascript revision makes the breaking changes needed to fix this. Or some sort of clever hack works around that constraint

The change is proposed for ECMAScript 6: http://wiki.ecmascript.org/doku.php?id=harmony:proper_tail_c...

GHCJS currently uses a trampoline, but all calls are in tail position, so when this gets implemented we can easily generate code that uses native JS tail calls.

Like GHC, GHCJS uses its own stack for non-tail calls.

I think native code GHC has its stack in the standard location, though it manages it explicitly (as most native code languages do). (I'll double check the ghc source later to make sure i'm quibbling correctly)