Displaying a string as another one

[Marcin Borkowski]

Hi all,

I have a buffer with long lines, containing many instances of strings
"\\n" and "\\t" (i.e., a literal backslash followed by "n" or "t").  I'd
like Emacs to display them as a newline and a tab, respectively.  These
instances occur inside strings (i.e., between quotes, which delimit
strings in JavaScript).

I tried
(setq prettify-symbols-alist '(("\\n" . ?\n) ("\\t" . ?\t)))
but this does not seem to work inside strings.

I suspect font-lock could do it, but I'm not sure how (and frankly,
I don't have time now to do many experiments).

Does anyone have a ready-made solution?

TIA,

-- 
Marcin Borkowski
http://mbork.pl