Ways to detect that XXXX in JSON \uXXXX does not correspond to a Unicode character?

[Richard Wordingham]

On Fri, 8 May 2015 05:08:21 +0200
Philippe Verdy <verdy_p at wanadoo.fr> wrote:

> Try by yourself, you can perfectly send JSON text containing '\uFFFF'
> (non-character) or '\uF800' (unpaired surrogate) and I've not seen
> any JSON implementation complaining about one or the other, when
> receiving the JSON stream and using it in Javascript, you'll see no
> missing code unit or replaced code units and no exception as well.

Unicode Consortium standards and recommendations allow non-characters
to be sent; as far as I can make out, they are just not to be thought of
as unstandardised graphic characters.

Richard.