Thanks for your help.
I have change the JavaScript command to Unicode big endian encoding. The FDF data is like below:
%FDF-1.2
1 0 obj<</Version/1.4/FDF<</Encoding/GBK/JavaScript<</After(? a p p . a l e r t \ ( ' a b c 1 2 3 ' \ ) ;)>>>>>>
endobj
trailer <</Root 1 0 R>> %%EOF
When opened the FDF data, the Adobe reader shows nothing. What wrong with the Javascript encoding?
Best regards.