gistfile1.js

var code = req.query.code, body = 'client_id=&client_secret=&grant_type=authorization_code&redirect_uri=https://localhost:3000/callback&code=' + code
        options = {
          method: 'POST',
          uri: 'https://alpha.app.net/oauth/access_token',
          form: body
        };

    request.post(options, function (err, res, body) {
      console.log(body);
    });