How should escaped unicode be handled by json parsers and encoders?

Question

The json spec allows for escaped unicode in json strings (of the form \\uXXXX). It specifically mentions a restricted codepoint (a noncharacter) as a valid escaped codepoint. Do

Answer 1

When you decode, it seems that this would be an appropriate use for the unicode replacement character, U+FFFD.

From the Unicode Character Database:

• used to replace an incoming character whose value is unknown or unrepresentable in Unicode
• compare the use of U+001A as a control character to indicate the substitute function