Simple cipher misses an illegal case.
Simple cipher misses an illegal case.

It was pass string like '123ABCxyz'.
arthurchipdean/xecmascript,tejasbubane/xecmascript,arthurchipdean/xecmascript,MattH-be/ecmascript,exercism/xecmascript,exercism/xecmascript,tejasbubane/xecmascript,MattH-be/ecmascript