Introduction to node.js GDD

Introduction to Node.js
Sudar Muthu (@sudarmuthu)
Research Engineer
Yahoo! Labs
http://github.com/sudar
http://sudarmuthu.com

Agenda
 What Node.JS is not
 What is Node.JS
 Why Node.JS?
 Using Node.JS
› As a interactive shell
› As a Server
› As a Client
 Common Modules
 Terminologies
 Workshop

Node.JS is not …

 Ruby on Rails
 Django
 Codeigniter
 CakePHP

Node.JS is bare bone and the community are making stuff like
Express, connect etc.

What is Node.JS
 JavaScript Programming Environment for creating highly
scalable network programs
 Provides Evented, non-blocking I/O
 Built on top of V8 engine
 Supports C/C++ based addons
 Supports CommonJS Module format
 Is fast .. in fact very fast.
 Similar to Event machine in Ruby or Twisted in Python

You can throw in more servers, but
that will cost you lot of money.

Single thread Asynchronous I/O

Why Node.JS?
So, code like this

var result = db.query("select..");
// use result

either blocks the entire process or
implies multiple execution stacks (threads).

Why Node.JS?
But code like this

db.query("select..", function (result) {
// use result
});

allows the program to return to the event loop immediately. No
more unnecessary threads.

Demo of Callback
// execute the callback after 2 seconds
setTimeout(function () {
console.log("World!");
}, 2000);

// print in console
console.log("Hello");

https://github.com/sudar/node.js-samples/blob/master/callback.js

Using Node.JS
 Install Node.JS
 Install NPM
 Install other modules you want by doing

npm install <module_name>

 You are good to go

(This setup is already done for you. Use the Ubuntu image in the
pen drive)

Node.JS – as an interactive shell
Similar to Python’s shell

$> node
>3+1
4
> true != false
true
>.help
>.exit

Node.JS – As a server
var http = require('http'); // require the http module

// create a server
http.createServer(function (req, res) {
// call this function when a request is received

res.writeHead(200, {
'Content-Type': 'text/plain'
});

// send this as part of the response
res.end('Hello Worldn');
}).listen(1337, "127.0.0.1"); // listen on port 1337

// debug information
console.log('Server running at http://127.0.0.1:1337/');

https://github.com/sudar/node.js-samples/blob/master/http-server.js

Node.JS – As a client
var http = require('http'); // require the needed modules

// make the request object
var request = http.request({
'host': 'sudarmuthu.com',
'port': 80,
'path': '/',
'method': 'GET'
});

// assign callbacks
request.on('response', function (response) {
console.log('Response Status Code: ' + response.statusCode);

response.on('data', function (data) {
console.log('Body: ' + data);
});
});

https://github.com/sudar/node.js-samples/blob/master/http-client.js

Core Modules

 Processes
 Filesystem
 Networking
 Utilities

The entire list can be found at http://nodejs.org/api/

Core Modules - Processes
Node allows you to analyze your process and manage external
process

Available Modules

 process
 child_process

Code samples: https://github.com/sudar/node.js-
samples/blob/master/process.js

Core Modules - Filesystem
Low level API to manipulate files

Available Modules

 fs
 path

Code Samples: https://github.com/sudar/node.js-
samples/blob/master/filesystem.js

Core Modules - Networking
Available Modules

 net
 dgram
 http
 tls
 https
 dns

samples/blob/master/dns.js

Core Modules - Utilities
Provides utility methods

Available Modules

 console
 util

samples/blob/master/console.js

Node.JS is useful for..
 Writing highly concurrent server applications
 Sharing application logic between server and client
 Peer-to-peer web applications using websockets
 Real-time applications

Terminologies
 NPM – Package manager (like apt-get)
 Modules – Plugins or add-ons for Node.JS
 Express – MVC framework (like RoR)
 Jade – Template Engine (like Smarty)
 Socket.IO – A websockets Library

Links
 http://github.com/sudar/node.js-samples (all code samples
used in this talk)
 http://nodejs.org
 http://npmjs.org
 http://expressjs.com
 http://socket.io

Express JS
 Basic web framework
 Runs on top of node.js
 Provides routing and redirection helpers
 Dynamic view helpers
 Has support for sessions
 Focus on high performance

Hello World Express App

https://github.com/sudar/node.js-samples/tree/master/express/hello-world

Square Things App
 Allows you to choose the color of a square region
 A very simple server implementation
 A very simple client MVC implementation
 Uses node.js on the server
 Uses Y.App implementation on the client

https://github.com/ericf/square-thing-app

Introduction to node.js GDD

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