Express 3.x: What's New, Release History & Support Lifecycle

What Is New in Express 3

How does Express 3 handle proxy headers and HTTPS detection?

Express 3 adds a trust proxy setting that makes req.protocol and res.redirect respect the X-Forwarded-Proto and X-Forwarded-For headers.

app.set('trust proxy', true);
app.get('/', function (req, res) {
  // req.protocol will be 'https' if X-Forwarded-Proto is 'https'
  res.send('Protocol: ' + req.protocol);
});

When the flag is on, req.ip also falls back to the first entry in req.ips, giving you the real client address behind a load balancer.

What new request helpers does Express 3 provide?

Express 3 ships with a richer req object that covers routing, content negotiation, caching and range parsing out of the box.

These helpers cut down on boilerplate; you no longer need external modules for basic content-negotiation or IP extraction.

How can I simplify response handling with Express 3's new methods?

Express 3 adds a suite of res utilities that let you set headers, negotiate content, and manage cookies without reaching for third-party libraries.

app.get('/data', function (req, res) {
  res.type('json');
  res.format({
    json: function () { res.json({ ok: true }); },
    html: function () { res.send('<h1>OK</h1>'); }
  });
});

Use res.locals to stash view data, res.links to emit RFC-5988 Link headers, and res.jsonp for explicit JSONP callbacks. Cookie handling now accepts objects directly, and signed cookies are a one-liner with { signed: true }.

Why should I use app.locals and res.locals in Express 3?

app.locals and res.locals give you a clean, template-friendly namespace that lives outside the request cycle.

Set global values once on the app:

app.locals.siteName = 'Acme Corp';

Then add request-specific data in a route:

app.get('/', function (req, res) {
  res.locals.user = req.user;
  res.render('home');
});

This avoids mutating req and keeps your view layer decoupled from middleware concerns.