Content-Type: image/jpeg
Content-Disposition: attachment; filename=genome.jpeg;
  modification-date="Wed, 12 Feb 1997 16:29:51 -0500";
Content-Description: a complete map of the human genome

app.get('/down2', function(req, res){
  var filename = 'data.csv';
  res.attachment(filename);
  res.end('hello,worldnkeesun,hi', 'UTF-8'); //Actually, the data will be loaded form db.
});