Unable to map routes file with ExpressJS Router

Question

I'm reading an intro book about ExpressJS and unfortunately they are using Express 3.x. I am trying to get their code example updated to Express 4.x. Here is their example:

routes/index.js

exports.index = function(req, res){
    res.send('welcome');
};

app.js

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

// Load the route handlers
var routes = require('./routes');

// Add router middleware explicitly
app.use(app.router);

// Routes
app.get('/', routes.index);

http.createServer(app).listen(3000, function(){
console.log('App started');
});

Here, app.router is deprecated and node throws an error about it. I have updated the code:

var http = require('http');
var express = require('express');
var app = express();
var bodyParser = require('body-parser');
var router = express.Router();

var routes = require('./routes');
router.get('/', routes.index);

app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());

http.createServer(app).listen(3000, function() {
    console.log('Express app started');
});

However, when visit localhost:3000 , I get this error displayed in the browser:

Cannot GET / 

If I remove usage of the Router class entirely (and remove app.use(app.router) ), I can just do:

app.get('/', routes.index);

and that will work.

How do I load my external route with the Router class?

Answer 1

In express 4, you construct your routes using routers.

So, say you have routes/index.js and routes/foo.js, they would look something like this:

// routes/index.js
var router = require('express').Router();

router.get('/', function(req, res){
  res.send('Hello!');
});

module.exports = router;

// routes/foo.js
var router = require('express').Router();

router.get('/bar', function(req, res){
  res.send('foobar');
});

module.exports = router;

In your main server file you can then app.use these routers, attaching them at various places. You could also do router.use to attach routers to routers (eg /users/user-id/pictures/picture-id kind of routes).

// server.js
var http = require('http');
var express = require('express');
var app = express();
var bodyParser = require('body-parser');

app.use('/', require('./routes/index'));

app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());

app.use('/foo', require('./routes/foo'));

app.listen(3000);

And you should now be able to GET / and GET /foo/bar.

---

For a bit more technical correctness, you should also be including middleware only on routes that need it.

You can do this per router, or per endpoint.

router.use(bodyParser.json());

// or

router.route('/baz')
  .use(bodyParser.json())
  .post(function(req, res){
    res.status(201).json(req.body);
  });

This is generally good to do, but also can be very important in some cases, eg handling file uploads.