I've been trying to make a simple site with Node.js, Express.js, and MongoDB. I'm new to these technologies and have been having problem set up the database
Here is snippet of code in my index.js file:

var http = require('http'),

    express = require('express'),

    path = require('path'),

    MongoClient = require('mongodb').MongoClient,

    Server = require('mongodb').Server,

    CollectionDriver = require('./collectionDriver').CollectionDriver;



var app = express();

app.set('port', process.env.PORT || 3000);

app.set('views', path.join(__dirname, 'views'));

app.set('view engine', 'jade');



var mongoHost = 'localHost';

var mongoPort = 27017;

var collectionDriver;



var mongoClient = new MongoClient(new Server(mongoHost, mongoPort));

mongoClient.open(function(err, mongoClient) {

  if (!mongoClient) {

      console.error(Error! Exiting... Must start MongoDB first);

      process.exit(1);

  }

  var db = mongoClient.db(MyDatabase);

  collectionDriver = new CollectionDriver(db);

});

After I try to run node index.js in terminal, it says the following:

js-bson: Failed to load c++ bson extension, using pure JS version



/Users/username/dev/ga-final/index.js:31

mongoClient.open(function(err, mongoClient) { //C

            ^

TypeError: Object #<MongoClient> has no method 'open'

at Object.<anonymous> (/Users/username/dev/ga-final/index.js:31:13)

at Module._compile (module.js:456:26)

at Object.Module._extensions..js (module.js:474:10)

at Module.load (module.js:356:32)

at Function.Module._load (module.js:312:12)

at Function.Module.runMain (module.js:497:10)

at startup (node.js:119:16)

at node.js:906:3

What is wrong? Why can't I call open? Can you help me fix this? thanks!