Node.js is a JavaScript runtime built on Chrome's V8 engine that allows building fast and scalable network applications in a non-blocking and event-driven way. It uses a single thread with callbacks and asynchronous I/O to handle multiple operations concurrently without blocking. Common uses of Node.js include real-time applications, streaming, process monitoring, and building JSON APIs. It is not suited for CPU-intensive or data transformation tasks.

1. node.js dao
Vova Miguro

2. What’s it all about?

3. Node.js is a platform built on
Chrome’s JavaScript runtime for
easily building fast, scalable
network applications.
-nodejs.org

4. How?
Let’s keep slow operations
from blocking other
operations.

5. traditional I/O
var data = file.read(‘image.png’);
//zzz...
doSomething(data);
something not right here...

6. async I/O
file.read(‘image.png’,function(data){
doSomething(image);
});
doSomethingElse();
profit!

7. callback()
callback()
callback()

8. node.js internals
• v8 (yeah, it’s Chrome’s engine)
• libev (event loop)
• libeio (asynchronous version of
POSIX API)

9. it is only one thread!
file.read(‘file.txt’,function(data){
//will never fire...
})
while(true){
//blocking entire process
}

10. http server
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello Worldn');
}).listen(3000);

11. watch file
var fs = require('fs');
fs.watchFile('system.log',function () {
console.log('log changed!');
});

14. node & mongo
var mongodb = require('mongodb');
var server = new Server('127.0.0.1', 27017, {});
new Db('test', server, {}).open(function (error, client) {
var collection = new Collection(client, 'tmp');
//insert doc
collection.insert({a:12,b:'string'},{},function(){
//find doc
collection.find({}, {limit:10}).toArray(function(err, docs) {
//do smth with docs
});
});

15. node & web sockets
//server
var io = require('socket.io').listen(80);
io.sockets.on('connection', function (socket) {
socket.emit('news', {hello:'world'});
});
//client
var socket = io.connect('http://localhost');
socket.on('news', function (data) {
console.log(data);
});

16. let’s see...

17. suited for...
• real time
• streaming
• process monitoring
• JSON API’s

18. do not use for this...

19. do not use for this...
• CPU heavy apps
• data transformation

20. ?