Node.JS

V8

• JavaScript-Engine von Google
• Opensource-Projekt (C++)
• ECMAScript 3-kompatibel
• Verdammt schnell (JIT-Compiler)

Empfehlung

http://www.slideshare.net/simon/a-reintroduction-to-javascript

Empfehlung

Douglas Crockford "JavaScript: The Good Parts"

Argumente

• klein & einfach
• dynamisch
• objektorientiert
• allgegenwärtig

Argumente

• klein & leichtgewichtig
• gleiche Sprache wie im Browser
• asynchrones I/O
• HTTP-Client und -Server
• keine Threads

Installation
# download
$ git clone git://github.com/ry/node.git

# compile
$ cd node
$ ./configure
$ make

# run
$ ./node hello.js

# read doc
$ man doc/node.1

Hallo Welt (Konsole)

// import module
var sys = require("sys");

// greet the world
sys.puts("Hallo, Welt");

12

Hallo Welt (Server)

// import module
var http = require("http");

// create an HTTP server on port 8000
http.createServer(function(req, res) {
res.sendHeader(200, {"content-type": "text/plain"});
res.sendBody("Hallo, Welt");
res.finish();
}).listen(8000);

13

Promises
// import module
var sys = require("sys");
var posix = require("posix");

// load a file
var promise = posix.open("file.txt", posix.O_RDONLY);
promise.addCallback(function(fd) {
var promise = posix.read(fd, 1024, 0, "utf-8");
promise.addCallback(function(data) {
sys.puts(data);
posix.close(fd);
});
});

// shortcut
var data = posix.cat("file.txt").wait();

14

Echo-Server
var tcp = require("tcp");

var server = tcp.createServer(function (socket) {
socket.setEncoding("utf8");
socket.addListener("connect", function () {
socket.send("hellorn");
});
socket.addListener("receive", function (data) {
socket.send(data);
});
socket.addListener("eof", function () {
socket.send("goodbyern");
socket.close();
});
});
server.listen(7000);

Server mit URL-Dispatcher
// fu.js
var server = createServer(function(req, res) {
if (req.method == "GET") {
(getPaths[req.uri.path] || notFound)(req, res);
}
});

function notFound(req, res) {
res.sendHeader(404, { "content-type": "text/plain" });
res.sendBody("Not Found"); res.finish();
}

exports.listen = function(port) {
server.listen(port || 8080);
};

exports.close = server.close;

17

Handler registrieren
// fu.js
var getPaths = {};

exports.get = function(path, handler) {
getPaths[path] = handler;
};

// chat.js
var fu = require("fu");
fu.get("/", function(req, res) { ... });
fu.get("/style.css", fu.staticHandler("style.css"));
fu.listen();

18

Beispiel-Handler
// fu.js
exports.staticHandler = function(filename) {
var contentType = _contentType(filename);
var encoding = _encoding(contentType);
return function(req, res) {
var promise = posix.cat(filename, encoding);
promise.addCallback(function(data) {
res.sendHeader(200, {
"content-type": contentType,
"content-length": data.length
});
res.sendBody(data);
res.finish();
});
};
};

19

join & part
// chat.js
fu.get("/join", function(req, res) {
var nick = req.uri.params["nick"];
var session = createSession(nick);
channel.addMessage("join", nick, "");
res.json(200, {id: session.id, nick: nick});
});

fu.get("/part", function(req, res) {
var session = sessions[req.uri.params["id"]];
session.destroy();
res.json(200, {});
}

20

create sessions
// chat.js
var sessions = {};

function createSession(nick) {
var session = {
id: Math.floor(Math.random() * 99999999999),
nick: nick,
timestamp: new Date(),
destroy: function() {
channel.addMessage("part", this.nick);
delete sessions[this.id];
}
};
return sessions[session.id] = session;
}

21

get users & send message
// chat.js
fu.get("/who", function(req, res) {
var nicks = _.map(sessions, function(s) {
return s.nick;
});
res.json(200, {nicks: nicks});
});

fu.get("/send", function(req, res) {
var session = sessions[req.uri.params.id];
channel.addMessage("msg",
session.nick,
req.uri.params.text);
res.json(200, {});
});

22

add & dispatch message
// chat.js
var channel = {
messages: [],
callbacks: [],

addMessage: function(cmd, nick, text) {
var m = {cmd: cmd, nick: nick, text: text};
this.messages.push(m);
for (var i in callbacks) {
this.callbacks[i](m);
}
}
...
};

23

get old messages

// chat.js
fu.get("/get", function(req, res) {
var session = sessions[req.uri.params.id];
var since = parseInt(req.uri.params.since, 10);
channel.query(since, function(messages) {
res.json(200, {messages: messages});
});
});

24

get msg & register interest
// chat.js
var channel = {
...,
query: function(since, callback) {
var matching = [];
for (var i in messages) {
if messages[i].timestamp > since)
matching.push(messages[i]);
}
if (matching.length > 0) {
callback(matching);
} else {
callbacks.push(callback);
}
}
};

25

cleanup

setInterval(function () {
var now = new Date();
while (callbacks.length > 0 &&
now - callbacks[0].timestamp > 30*1000) {
callbacks.shift().callback([]);
}
}, 1000);

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