Not necessarily, since their GC semantics might differ from JavaScript. For example, if they have finalizers, then compiling into JS isn't an option. Other sem

Not necessarily, since their GC semantics might differ from JavaScript. For example, if they have finalizers, then compiling into JS isn't an option. Other semantic differences might also make this hard or impossible. Compare pyjamas to pypy.js, for example - the former compiles to JS, but has known differences from proper Python semantics (long bignums), while the latter is a straight port of a Python VM, so the semantics are identical.