var StringifyObjectTransform = require('stringify-object-transform');
require('http').createServer(function(request, response) {
  response.statusCode = 404;
  // ...
  .once('data', function() {
    response.statusCode = 200;
    response.setHeader('Content-Type', 'application/json');
  })
  .pipe(new StringifyObjectTransform())
  .pipe(response);
});