gistfile1.js

var db = new mongo.Db('myDB', new mongo.Server("localhost", "27017", {})),
    to = "ralph";

db.open( function( err, p_client ) {

    // Problem opening the database?
    if ( err ) {
        console.log( "db.open: " + err );
    }

    // Open the users collection
    db.collection( 'users', function( err, collection ) {

        // Retry if no collection was found
        if ( err || ( ! "findOne" in collection )) {
            console.log("db.collection: " + err );
        } else {

            // Let's find our user
            collection.findOne({
                "addresses.localPart" : to
            }, function( err, doc ) {

                if ( err ) {
                    console.log( "collection.findOne: " + err );
                }

                console.log( "doc: " + doc );
              
            });      
        }
    });
});