Express 4.x: What's New, Release History & Support Lifecycle

What Is New in Express 4

Why does Express 4 no longer bundle middleware?

Express 4 stopped bundling any Connect middleware because the core team wanted to keep the framework lightweight and let npm handle updates.

In practice you now list each piece (body-parser, cookie-parser, etc.) in package.json and install it separately. This means security patches land faster and you only ship what you actually use.

How do I replace the old app.use(app.router) pattern?

You no longer call app.use(app.router); routes are added in the exact order you declare them.

Because Express now respects declaration order, mixing middleware and route handlers works intuitively:

app.get('/', home);
app.use('/public', require('st')(process.cwd()));
app.get('/users', users.list);
app.post('/users', users.create);

Think of it as a single queue: each app.use or verb pushes a handler onto the tail, and requests flow through that queue.

What is the app.route() shortcut and how does it simplify code?

app.route() lets you chain HTTP verbs for a single path, cutting duplication.

app.route('/users')
  .get(function(req, res, next) {
    // handle GET /users
  })
  .post(function(req, res, next) {
    // handle POST /users
  });

All middleware attached to the chain runs only for /users, so you avoid repeating the path string in every verb.

How can I organize routes with the new express.Router?

The new express.Router works like a mini-app, so you can split each resource into its own file.

var express = require('express');
var people = express.Router();

people.use(function(req, res, next) {
  // router-level middleware
  next();
});

people.get('/', function(req, res) {
  res.send('People index');
});

module.exports = people;

Mount it in the main app with app.use('/people', require('./routes/people'));. This mirrors the way you'd structure a large Express 3 app but with a cleaner, dependency-free core.