What Is New in Express 2
| Category | Change |
|---|---|
| New Features | res.json() - explicit JSON response; chainable res.status(code); res.locals(obj) and res.local(name,val); app.lookup.VERB() and app.match.VERB() shortcuts; app.VERB() alias; app.param() now accepts multiple callbacks; strict routing setting; case-sensitive routes option; basepath setting for reverse proxies; support for PURGE method; res.contentType literal forms; second-callback support for res.download; options support for res.clearCookie. |
| Improvements | View cache defaults to enabled in production; default charset set to utf-8; default cookie path set to "home"; added request, response and app locals; added settings local variable; req.flash now throws if session missing; added req.get(field,param); added req.accepts() extensions; added req.path shortcut; res.helpers alias for res.locals(); res.send(bool) now returns JSON; res.send(undefined) yields 204. |
| Bug Fixes | Fixed res.redirect HEAD support; fixed res.sendfile bug with spaces in filenames; fixed res.send(undefined) 204 response; fixed view caching collisions across multiple apps; fixed partial lookup precedence; fixed app.all duplicate DELETE handling; fixed app.param callback execution per route middleware; fixed res.header set intention when value undefined; fixed req.is() charset handling; fixed multiple-param callback regression; fixed res.redirect on Windows path joins. |
| Deprecations | Removed request and response locals (now only app.locals); removed stream threshold setting. |
| Breaking Changes | View engine signature changed to engine.compile(str, options) returning a render function; default view cache now enabled in production (affects dev workflow); default charset switched to utf-8; removal of request/response locals may break code that relied on them; view engine .filename option no longer used. |
How do I send JSON responses with the new res.json helper?
Use res.json() to send a JSON payload without worrying about content-type or charset.
It automatically sets Content-Type: application/json; charset=utf-8 and stringifies the object.
app.get('/api/user', function(req, res){\n var user = { id: 7, name: 'Ada' };\n res.json(user);\n});Before Express 2 you would write res.send(user) and rely on type detection; now res.json is the explicit, future-proof way.
What are the new routing shortcuts app.lookup, app.match, and app.VERB?
Express 2 adds three helpers that let you query or invoke routes without a full request.
app.lookup.VERB(path)returns the route object for a given HTTP verb.app.match.VERB(path)returns true/false if a route matches.app.VERB(path)is a shorthand forapp.lookup.VERB(path).
These are handy for feature flags, conditional middleware, or testing route existence.
// check if a GET route exists for /admin\nif (app.match.get('/admin')) {\n console.log('admin route is defined');\n}\n\n// retrieve the route object for POST /login\nvar postLogin = app.lookup.post('/login');\nconsole.log(postLogin.stack.length); // number of middleware functionsWhich view engine changes will break my existing templates?
Express 2 changes the view engine API: engines must now export a compile(str, options) function that returns a render function.
Older engines that exported engine.render(str, options, callback) will throw at runtime.
In practice you need to update custom engines or upgrade third-party ones to the new compile signature.
Additionally, view caching is enabled by default in production, and the default charset is now utf-8, so templates that relied on the previous defaults may render differently.
How do strict routing and case sensitivity affect my route definitions?
Enable app.set('strict routing', true) to make trailing slashes matter and app.set('case sensitive routing', true) to make path case matter.
With strict routing, /users and /users/ are distinct; without it they are treated as the same route.
Case sensitivity means /API will not match a handler defined for /api.
app.set('strict routing', true);\napp.set('case sensitive routing', true);\n\napp.get('/api', function(req, res){ res.send('lowercase'); });\n// GET /API will now 404This is useful for APIs that need precise URL contracts, but most apps can keep the defaults for flexibility.
Common Questions
Does Express 2 require changes to my view engine implementation?
Yes, view engines must now provide a compile(str, options) function that returns a render function.
How do I enable strict routing?
Call app.set('strict routing', true) before defining your routes.
Can I still use req.flash without a session?
No, req.flash now throws an error if req.session is missing.
What is the new way to send a JSON response?
Use res.json(yourObject) which automatically sets the correct content type and charset.
How do I define a route that handles all HTTP verbs?
Use app.all(path, handler) which registers the handler for every method.