Use do-while instead of tail recursion

[minuteman3]

Since javascript doesn't do tail call elimination a recursive solution still builds up a big pile of stack frames (one per character) each containing a string (ch) that doesn't get garbage collected until the whole thing has returned. It's trivial to replace tail recursion with a do-while loop which doesn't suffer from the negative effects.

[minuteman3]

I suppose blocking the event loop isn't a great idea, maybe the fact that it's "sync" got me carried away.

[heapwolf]

yeah, even tough theres an unbound callstack it has a reasonably short lifetime :)