callback.js

var consumer = require('../lib/twitter')

module.exports = function(req, res) {
  consumer.getOAuthAccessToken(req.session.oauthRequestToken, req.session.oauthRequestTokenSecret, req.query.oauth_verifier, function(error, oauthAccessToken, oauthAccessTokenSecret, results) {
    if (error) {
      res.send("Error getting OAuth access token")
      console.log(error)
    } else {
      req.session.oauthAccessToken = oauthAccessToken
      req.session.oauthAccessTokenSecret = oauthAccessTokenSecret
      
       consumer.get("http://twitter.com/account/verify_credentials.json", req.session.oauthAccessToken, req.session.oauthAccessTokenSecret, function (error, data, response) {
        if (error) {
          res.send("Error getting Twitter Username")
          console.log(error)
        } else {
          var parsedData = JSON.parse(data)
          req.session.name = parsedData.screen_name
          res.redirect("/")
        } 
      });
    }
  });
}