app.js

var connect = require("connect"),
	express	= require("express");
	
var app 	= express.createServer(),
	routes 	= require("./routes");

app.configure(function(){
    app.set("views", __dirname + "/views");
    app.use(app.router);
});

app.routes = routes( app, function(){ 
	app.listen(  300 ); 
});

routes-notworking.js

var mongo = require('mongodb'),
 db = new mongo.Db( "dataset", new mongo.Server( "localhost", 1234, {} ), {} );


function applicationRouter( app, serverCallback ){
db.open(function(){
		app.get("/", function( req, res, next ){
			res.writeHead(200, {
				'Content-Type': 'text/html',
			});
			res.end("Hello world");
		});
		serverCallback();
}):
		
};
module.exports = applicationRouter;

routes-working.js

var mongo = require('mongodb'),
 db = new mongo.Db( "dataset", new mongo.Server( "localhost", 1234, {} ), {} );


function applicationRouter( app, serverCallback ){
		app.get("/", function( req, res, next ){
			res.writeHead(200, {
				'Content-Type': 'text/html',
			});
			res.end("Hello world");
		});
		serverCallback();
		
};
module.exports = applicationRouter;