Simple Post formData with node.js and request keep failing

Question

I am trying to post data with a file to remote server using node.js and request module, the code send the data without the file. I use the docs example https://github.com/request/request#forms

I can post the same data with php curl with the code below , so I know the remote server code works.

What am I doing wrong?

$post = array(
    'sessionId' => 1234,
    'source' => 'text',
    'files[jpg]' => '@' . $file_name_with_full_path
);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $target_url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

$result = curl_exec($ch);
curl_close($ch);

My node.js code

var fs = require("fs");
var formData = {
    sessionId: 1234,
    source: 'text',
    files: JSON.stringify (
              {jpg:  fs.createReadStream( __dirname +"/"+ file.txt)}
      )
  request.post({url: 'https://url', formData: formData}, 
    function optionalCallback(err, httpResponse, body) {

    });

Answer 1

This code successfully posted the file.

  var r = request.post('https://url', function optionalCallback(err,httpResponse, body) { })
    var form = r.form();
    form.append('sessionId', 1234);
    form.append('source', 'text');
    form.append('file[jpg]', fs.createReadStream( __dirname +"/"+ file.txt);