res.download() not working in my case

I am using nodejs and expressjs framework to download a file 'jsonFile.json' from server.

i am using the following code

res.get('/download', function(req, res) {
         res.setHeader('Content-disposition', 'attachment; filename=jsonFile.json');
          res.setHeader('Content-Type', 'text/json');
          res.download(__dirname + 'jsonFile.json');
        }
      });

But this results into a response with whole content of file.

i was expecting browser to ask me to save the file in local disk.

How do i save the file in local disk.???

Let Express set the correct headers and just do this:

res.get('/download', function(req, res) {
  res.download(__dirname + 'jsonFile.json', 'jsonFile.json');
});

(doc)

EDIT: since you're requesting /download through an AJAX call, you have to change your setup because most (all?) browsers will not show a download dialog in that case.

Instead, you can create a new window from your front end code to trigger the dialog:

window.open('/download?foo=bar&xxx=yyy');

Just to confirm what @robert said,

because this thing turned my head for two days, instead of using an ajax call, open a new window with your ajax request location, for example:

window.open("http://yourserver.com/api/link?a=3&b=4")

hope this helps someone.