node.js - How to change the default error output in restify -

is there way can change default error output? i'm going change rest error output:

{     "code": "invalidargumenterror",     "message": "blah blah..." } 

to:

{     "code": 10001,     "message": "blah blah",     "extramsg": "blah blah" } 

here of ideas:

• listen error events.
  seems not resterror have emitted events (like notfound, methodnotallowed, versionnotallowed... do). can't catch errors rewrite them.

• listen event before response data sent.
  through official documents , have found nothing relative.

• modify implementation of resterror class.
  it's not approach.

any other ideas?

finally provide customized json formatter want:

var server = restify.createserver( {     formatters: {         'application/json': function customizedformatjson( req, res, body ) {             // copied restify/lib/formatters/json.js              if ( body instanceof error ) {                 // snoop resterror or httperror, don't rely on                 // instanceof                 res.statuscode = body.statuscode || 500;                  if ( body.body ) {                     body = {                         code: 10001,                         scode: body.body.code,                         msg: body.body.message                     };                 } else {                     body = {                         code: 10001,                         msg: body.message                     };                 }             } else if ( buffer.isbuffer( body ) ) {                 body = body.tostring( 'base64' );             }              var data = json.stringify( body );             res.setheader( 'content-length', buffer.bytelength( data ) );              return data;         }     } } );