JS: avoid head/tail and unpackFS
Related to !9290 (closed): avoid the use of head and tail in one easy case where we can avoid it.
Also avoid the use of unpackFS if we can and use Ppr.ftext instead of Ppr.text.
Related to !9290 (closed): avoid the use of head and tail in one easy case where we can avoid it.
Also avoid the use of unpackFS if we can and use Ppr.ftext instead of Ppr.text.