Replace isspace.

Json Object define its own white space.
ws = *(
  %x20 /              ; Space
  %x09 /              ; Horizontal tab
  %x0A /              ; Line feed or New line
  %x0D                ; Carriage return
)
Export override operator [] for json object

Two functions to export.
1) operator[size_t pos] const;
2) operator[const string& key] const;