app.get('/refresh_token', function(req, res) {

  // requesting access token from refresh token
  var refresh_token = req.query.refresh_token;
  var authOptions = {
    url: 'https://accounts.spotify.com/api/token',
    headers: { 'Authorization': 'Basic ' + (new Buffer(client_id + ':' + client_secret).toString('base64')) },
    form: {
      grant_type: 'refresh_token',
      refresh_token: refresh_token
    },
    json: true
  };

  request.post(authOptions, function(error, response, body) {
    if (!error && response.statusCode === 200) {
      var access_token = body.access_token;
      res.send({
        'access_token': access_token
      });
    }
  });
});


document.getElementById('obtain-new-token').addEventListener('click', function() {
            $.ajax({
              url: '/refresh_token',
              data: {
                'refresh_token': refresh_token
              }
            }).done(function(data) {
              access_token = data.access_token;
              oauthPlaceholder.innerHTML = oauthTemplate({
                access_token: access_token,
                refresh_token: refresh_token
              });
            });
          }, false);