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

[Doug Ewell]

I interpreted Roger Costello's original question literally, that he
wanted to find instances of '\uXXXX' that do not represent an ASSIGNED
Unicode character. Apologies if this discussion is really about
something else.

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Doug Ewell | http://ewellic.org | Thornton, CO ����