gistfile1.txt

//
// Lets take as example the next Mongodb URI
// mongodb://nodejitsu:[email protected]:10047/nodejitsudb54463349176
// mongodb://username:passwd@hostname:port/datababaseName
// 
// So the code should looks like
 var mongodb = require('mongodb');
 var db = new mongodb.Db('nodejitsudb544633491762',
   new mongodb.Server('alex.mongohq.com', 10047, {})
 );
 db.open(function (err, db_p) {
   if (err) { throw err; }
   db.authenticate('nodejitsu', '684e3def50116af8c8ab032f65230fac', function (err, replies) {
     // You are now connected and authenticated.
   });
 });