Express 3.0是一个维护版本，针对2.x版修复了很多问题，并加入了很多新功能。
在使用Express框架时，要记住，Express框架是帮助开发者快速实现HTTP通信相关的功能，而不是成为像Rails那样功能强大、全面的框架。
Connect 2.x
Changes introduced by Connect 2.x:
added err.status support to Connect’s default end-point
added session() “proxy” setting to trust “X-Forwarded-Proto”
added cookieSession() middleware
added compress() middleware for gzipped responses
added multipart() middleware
added json() middleware
added urlencoded() middleware
added limit option to the three above middleware
added defer option to multipart() to listen on formidable’s events
added debug() instrumentation to aid in debugging
changed basicAuth()’s req.remoteUser to req.user
changed session() to only set-cookie on modification (hashed session json)
changed bodyParser() to be an aggregate of json(), multipart() and urlencoded()
moved many cookie-related utils into npm
moved static()’s logic into a separate npm module named “send”
increase perf ~%20 by memoizing url parsing
removed router() middleware
fixed default encoding for logger(), now “utf8” instead of “ascii”
fixed mount-path case-sensitivity
Connect docs are available at http://www.senchalabs.org/connect/, and will eventually be mirrored on expressjs.com as well for convenience, along with usage guides.
作者：chszs，转载需注明。作者博客主页：http://blog.csdn.net/chszs
Express 3.x
Changes introduced by Express 3.x:
added several new examples in ./examples
added unit testing for the examples (most of them at least)
added res.jsonp() to explicitly opt-in to JSONP support
added ETags and conditional-GET handling to res.send() responses
added “jsonp callback name” setting
added support for status code as first or second arg to res.send() and res.redirect()
added req.range(size) to parse Range header fields
added req.auth for basic auth
added res.links(obj) to set response the Link header field for pagination
added res.format(obj) for content-negotiation
added req.fresh for conditional-GETs
added req.stale for conditional-GETs
added mount-point relative redirection support to res.redirect()
added req.ip for the remote address (supporting reverse proxies)
added req.ips for remote address(es) (supporting reverse proxies)
added [] support in jsonp callback
added app.get(name) to compliment app.set(name, val)
added app.engine() to register template engines (replaces app.register())
added req.subdomains to return an array of subdomains
added req.protocol to return the request protocol string (“http” or “https”)
added req.secure to assert that req.protocol is “https”
added req.path to return the parsed url’s pathname
added req.host to return hostname (Host void of port)
added debug() instrumentation to aid debugging
added req.accepts()
added req.acceptsLanguage()
added req.acceptsCharset()
added req.accepted
added req.acceptedLanguages
added req.acceptedCharsets
added “json replacer” setting to manipulate json responses (remove private keys etc)
added “json spaces” setting to compress or expand json as you like (defaults to 2 in dev)
added express.application prototype
added express.request prototype
added express.response prototype
added app.render() for app-level templates
added res.type() to replace old res.contentType()
added { signed: true } option to res.cookie()
added async signature to res.render(), engines in consolidate.js work OOTB
removed partial()
removed express-level layout support (engines provide similar)
renamed “case sensitive routes” to “case sensitive routing”
removed res.signedCookie()
removed “root” setting
removed res.redirect('home') support
removed req.notify()
removed app.register()
removed app.redirect()
removed app.is()
removed app.helpers()
removed app.dynamicHelpers()
Head over to the New Features in 3.x wiki page for a more comprehensive list of additions, or to 3.x migration to help you upgrade if you wish to do so.
