I don't think (s)he was implying it was using a plugin or anything.
An occasional feature of other languages-in-Javascript is some kind of sandboxing for security - eg the Valija Javascript subset that runs in the Caja sandbox (which in turn is implemented in Javascript): http://code.google.com/p/google-caja/wiki/SubsetRelationship...
Yes. Rather, I meant, which libraries were available. I figured that it'd at least have the core stdlib; that was just my first step exploring. It's a bad sign that the first statement I tried didn't work, though.