Express supports multiple options for application structure. Extracting elements of an Express application into separate files is one option; a good candidate for this is routes.

Let's extract our route heartbeat into ./lib/routes/heartbeat.js; the following listing simply exports the route as a function called index:

exports.index = function(req, res){
  res.json(200, 'OK'),
};

Let's make a change to our Express server and remove the anonymous function we pass to app.get for our route and replace it with a call to the function in the following listing. We import the route heartbeat and pass in a callback function, heartbeat.index:

var express = require('express')
  , http = require('http')
  , config = require('../configuration')
  , heartbeat = require('../routes/heartbeat')
  , app = express();

app.set('port', config.get('express:port'));
app.get('/heartbeat', heartbeat.index);

http.createServer(app).listen(app.get('port'));
module.exports = app;