Your code:
- Escapes characters unnecessarily (such as forward slash).
- Escapes using more characters than needed, making the JSON longer (using hex notation instead of simple backslash-escaping).
- Escapes every high Ascii character as \u00__ which is not only longer than \x__ but completely ignores the first byte of Unicode characters, making the result meaningless.
- Has goofy stuff like "- &hC2C0" which is clearly an undefined operation to perform on Unicode between &hC380 and &hC3BF. Perhaps you're matching character sets to character sets, but this is something you're supposed to solve with fonts, not subtraction to turn one code into another. To make your preposterous claim "This stuff has been tested and works for all characters so everything can be transfered with JSON now" valid, you have to rip out this junk. I don't care how elaborate a character map you use, you'll still be altering characters, hardly the desire of most people who want to send Unicode characters through JSON from ASP.

Here is my version:

[asp]Function JSONEscape(json)
Dim Pos
Dim Char
Dim Code
JSONEscape = ""
If IsNull(json) Then Exit Function
For Pos = 1 To Len(json)
Char = Mid(json, Pos, 1)
Code = AscW(Char)
If (Code >= 32 And Code <= 127) And Code 34 And Code 39 And Code 60 And Code 92 Then 'printable, plus skip '"\ and to avoid false HTML tags 0 Then
JSONEscape = JSONEscape & "\" & VBA.Mid("bfnOrtv'""\", Code, 1)
Else
Code = AscW(Char)
If (Code >= 0 And Code <= 255) Then 'escape nonprinting, high ascii, and < characters (to avoid false HTML tags)'
JSONEscape = JSONEscape & "\x" & VBA.Right("0" & Hex(Code), 2)
Else
JSONEscape = JSONEscape & "\u" & VBA.Right("000" & Hex(Code), 4)
End If
End If
End If
Next
End Function[/as]

I'm having a problem converting the string back to special characters. When I get data from JSON and the strings are escaped, and I need to put that data into a form field the \uuxx numbers are still there instead of the special characters. Do you have, or know of any function that reverses this process?

Erik