2. What is node.js? Why another server side technology? Node.js is a server-side JavaScript environment that uses an asynchronous event-driven model. This allows Node.js to get excellent performance based on the architectures of many Internet applications. Most regular Web Servers like Apache uses OS threads for request handling. That means that every request the server handles will spawn a OS thread and the web server won't release the thread until the request finish. Most of the time OS threads wait till some I/O operation finish: var result = query("select * from users"); for(user in result){ //You get the idea } In this case the OS thread just sits and waits the I/O operation returns to resume the flow. Every OS thread takes some memory, so regular servers can't handle many simultaneous connections without penalizing the system performance.
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5. hands on code: hello world! <?php //helloworld.php echo "hello"; sleep(2); echo "world!"; ?> //helloworld.js setTimeout(function(){ console.log("world!"); }, 2000); console.log("hello"); There is no waisted time on the node program, the thread is idle not waiting
6. hands on code: http server var http = require("http") ; var server = http.createServer(function(req, res){ res.writeHead(200, {"content-type":"text/plain"}); res.end("Hello World!"); }).listen(8000); Headers of the request are: HTTP/1.1 200 OK content-type: text/plain Connection: keep-alive Transfer-Encoding: chunked
7. hands on code: not only http var net = require("net") ; net.createServer(function(socket){ socket.on("data", function(data){ socket.write(data); }); }).listen(8000);
8. hands on code: telnet chat var net = require("net"); var clients = []; net.createServer(function(socket){ clients.push(socket); socket.on("data", function(data){ for(var i = 0; i < clients.length; i++){ if(clients[i] == socket) continue; clients[i].write(data); } }); socket.on("end", function(){ var index = clients.indexOf(socket); clients.splice(index, 1); }); }).listen(8000);
9. hands on code: Async I/O var fs = require("fs") , sys = require("sys");; fs.readFile("/home/cherta/workspace/samples/foo.txt", function(err, data){ if(err) throw err; sys.puts(data) }); console.log("Antes de foo?");
10. What is node.js? It's a set of tools and libraries living on top of the V8. What is not node.js? A super framework that would change your life. Assuming that your life will change for a crappy piece of software
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13. Socket I/O Socket.IO is a Node.JS project that makes WebSockets and realtime possible in all browsers. It also enhances WebSockets by providing built-in multiplexing, horizontal scalability, automatic JSON encoding/decoding, and more.
