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• Cygwin build is no longer supported. Use native windows builds instead.

• Buffer

  • The length optional third parameter was added to Buffer.write()

• child_process

  • The customFds option to the child_process.spawn() method is deprecated. Only the values -1, 0, 1, 2 will work with customFds now and only if those are TTY file descriptors. You can however use the stdinStream, stdoutStream, and stderrStream options to achieve similar functionality.
  • You can no longer send a file descriptor through a unix pipe. Instead you can send a handle via child_process.fork().

• The .pid property is not set to null when the child process exits. Listen for the 'exit' event instead.

• dgram

  • The 'unix_dgram' type to the dgram.createSocket() is no longer supported. Use bnoordhuis/node-unix-dgram instead. Note: The Unix domain datagram is not the Internet domain datagram (UDP) which stays supported.

• dns

  • dns.lookup() now uses getaddrinfo() in a thread pool instead of c-ares. The rest of the methods in the DNS module still use c-ares. Using the system resolver for common look ups is useful because it hooks into system MDNS lookups and /etc/host files and nsswitch, etc. Previously when using dns.lookup on invalid domain names like "****" the command returned an EBADNAME error. getaddrinfo() does not differentiate between invalid domains and ENOTFOUND (AKA NXDOMAIN). Therefore dns.lookup now returns ENOTFOUND when given malformated domain names like "*****".

• events

  • C++ node::EventEmitter has been removed. Instead use node::MakeCallback()
  • EventEmitter.removeAllListeners() allows to remove all listeners at once.

• fs

  • mode argument of fs.mkdir() and fs.mkdirSync() became an option (defaults to 0777).
  • fs.symlink() takes an optional mode argument, which can either be 'dir' or 'file'. The default is 'file'. This argument is only needed for Windows (it's ignored on other platforms).

• http

  • http.request() and http.get() use Connection: Keep-Alive by default.
  • http.Agent.appendMessage() was removed.
  • http.getAgent() was removed. Use http.globalAgent instead.
  • Not http.Agent but http.ClientRequest emits 'upgrade' event.

• https

  • https.request() and https.get() with default Agent ignore key, cert and ca options. Use custom Agent.

• Module system

  • The require.paths have been removed (use NODE_PATH environment variable instead).

• net

  • net.Server.listenFD() was no longer supported.

• process

  • process.ENV was removed. Use process.env instead.

  • process.ARGV was removed. Use process.argv instead.

  • process.binding('stdio') was removed. This was a private API. You shouldn't have been using it in the first place.

  • process.binding('net') was removed.

  • process.memoryUsage().vsize was removed. You don't need it.

  • process.stdout and process.stderr are blocking when they refer to regular files or TTY file descriptors.

  • process.stdin, process.stdout and process.stderr are getters now. You can override it (if you really want to) like this:

    process.__defineGetter__('stdout', function() {
      return your_object;
    });

• stream

  • stream.pipe() doesn't emit 'pause'/'resume' events on the source stream which doesn't implement pause()/resume().

• tty

  • tty.setWindowSize() was removed.
  • tty.getWindowSize(fd) was removed. Use process.stdout.getWindowSize() instead.

• V8 (v3.1 to v3.6)

  • RegExp was no longer a Function (compliant with ES5). Use RegExp.exec() instead.
  • Date's string format without timezone (e.g., new Date('2011-06-06')) has been based on UTC, not local timezone (compliant with ES5). Use timezone explicitly (e.g., new Date('2011-06-06 00:00:00 +09:00')).
  • All standard properties of Error have been made non-enumerable (compliant with ES5). use util.inspect(err, true) if you want to show it.

• assert
  • assert(val) as a shorthand for assert.ok(val)
• Buffer
  • 'hex' encoding.
  • Buffer.readInt8()/readInt16LE()/readInt16BE()/readInt32LE()/readInt32BE()
  • Buffer.readUInt8()/readUInt16LE()/readUInt16BE()/readUInt32LE()/readUInt32BE()
  • Buffer.readFloatLE()/readFloatBE()/readDoubleLE()/readDoubleBE()
  • Buffer.writeInt8()/writeInt16LE()/writeInt16BE()/writeInt32LE()/writeInt32BE()
  • Buffer.writeUInt8()/writeUInt16LE()/writeUInt16BE()/writeUInt32LE()/writeUInt32BE()
  • Buffer.writeFloatLE()/writeFloatBE()/writeDoubleLE()/writeDoubleBE()
  • Buffer.fill()
  • Typed Arrays
• child_process
  • child_process.fork()
• cluster
  • node cluster see http://nodejs.org/docs/latest/api/cluster.html
• crypto
  • crypto.createDiffieHellman(), crypto.pbkdf2(), crypto.randomBytes()
• fs
  • fs.watch()
  • fs.utimes()/utimesSync(), fs.futimes()/futimesSync()
  • start option to fs.createReadStream() and fs.createWriteStream().
• http
  • http.ClientRequest.setTimeout()/setNoDelay()/setSocketKeepAlive()
  • auth option to http.request().
• https
  • passphrase option to https.createServer(), https.request(), and https.get().
• Module system
  • .json module.
  • module.require()
• net
  • net.connect()
  • net.Socket.remotePort, bytesRead, bytesWritten
• os
  • os.arch(), os.platform(), os.uptime(), os.networkInterfaces()
• path
  • path.relative()
• process
  • process.arch, process.uptime()
• tls
  • passphrase option to tls.createServer() and tls.connect().
  • sessionIdContext option to tls.createServer().
  • tls.CryptoStream.getSession() and session option to tls.connect().
  • tls.CleartextStream.address(), remoteAddress, remotePort.
  • tls.Server supports NPN (Next Protocol Negotiation) and SNI (Server Name Indication).
• util
  • util.format(), util.isArray(), util.isRegExp(), util.isDate(), util.isError().
• zlib module http://nodejs.org/docs/latest/api/zlib.html