Dynamically requiring module in NodeJS

bar.js

exports.index = function(req, res) {
  res.send('This is bar!');
};

foo.js

exports.index = function(req, res) {
  res.send('This is foo!');
};

server.js

var express = require('express');
var app = express();

app.get('/', function(req, res) {
  res.send('Hi2u');
});

// dynamically require modules.
app.get('/:foo', function(req, res) {
  if (['foo', 'bar'].indexOf(req.params.foo) >= 0) {
    var foo = require('./lib/' + req.params.foo);
    foo.index(req,res);
  }
  else {
    res.send('endpoint not found');
  }
});

var server = app.listen(3000, function () {

  var host = server.address().address;
  var port = server.address().port;

  console.log('Example app listening at http://%s:%s', host, port);

});