Introduction to Node.js

The Server-side JavaScript

Vikash Singh

WHAT TO EXPECT AHEAD….
 Introduction
 Some (Confusing) Theory

 5 Examples

 A couple of weird diagrams

 2 Pics showing unbelievable benchmarks

 Some stuff from Internet

 And Homer Simpson

BACKGROUND
 V8 is an open source JavaScript engine developed
by Google. Its written in C++ and is used in Google
Chrome Browser.
 Node.js runs on V8.

 It was created by Ryan Dahl in 2009.

 Is still in Beta phase. Latest version is 0.6.11

 Is Open Source. It runs well on Linux systems, can
also run on Windows systems.
 If you have worked on EventMachine (Ruby) or
Python’s Twisted or Perl’s AnyEvent framework
then following presentation is going to be very easy.

INTRODUCTION: BASIC
 In simple words Node.js is ‘server-side
JavaScript’.
 In not-so-simple words Node.js is a high-
performance network applications
framework, well optimized for high concurrent
environments.
 It’s a command line tool.

 In ‘Node.js’ , ‘.js’ doesn’t mean that its solely written
JavaScript. It is 40% JS and 60% C++.
 From the official site:
‘Node's goal is to provide an easy way to build
scalable network programs’ - (from nodejs.org!)

INTRODUCTION: ADVANCED (& CONFUSING)
 Node.js uses an event-driven, non-blocking I/O
model, which makes it lightweight. (from
nodejs.org!)
 It makes use of event-loops via JavaScript’s
callback functionality to implement the non-
blocking I/O.
 Programs for Node.js are written in JavaScript but
not in the same JavaScript we are use to. There is
no DOM implementation provided by Node.js, i.e.
you can not do this:
var element = document.getElementById(‚elementId‛);
 Everything inside Node.js runs in a single-thread.

EXAMPLE-1: GETTING STARTED & HELLO
WORLD
 Install/build Node.js.
 (Yes! Windows installer is available!)
 Open your favorite editor and start typing
JavaScript.
 When you are done, open cmd/terminal and type
this:
‘node YOUR_FILE.js’
 Here is a simple example, which prints ‘hello world’
var sys = require(‚sys‛);
setTimeout(function(){
sys.puts(‚world‛);},3000);
sys.puts(‚hello‛);
//it prints ‘hello’ first and waits for 3 seconds and then
prints ‘world’

SOME THEORY: EVENT-LOOPS
 Event-loops are the core of event-driven
programming, almost all the UI programs use event-loops
to track the user event, for example: Clicks, Ajax
Requests etc. Clients send HTTP requests
Client
to Node.js server

Event loop returns An Event-loop is woken up by OS,
result to client passes request and response objects
Event loop to the thread-pool
(main thread)

Long-running jobs run
on worker threads
C++
Response is sent
Threadpool
back to main thread
(worker
via callback
threads)

SOME THEORY: NON-BLOCKING I/O
 Traditional I/O
var result = db.query(‚select x from table_Y‛);
doSomethingWith(result); //wait for result!
doSomethingWithOutResult(); //execution is blocked!

 Non-traditional, Non-blocking I/O
db.query(‚select x from table_Y”,function (result){
doSomethingWith(result); //wait for result!
});
doSomethingWithOutResult(); //executes without any
delay!

WHAT CAN YOU DO WITH NODE.JS ?
 You can create an HTTP server and print ‘hello
world’ on the browser in just 4 lines of JavaScript.
(Example included)
 You can create a TCP server similar to HTTP
server, in just 4 lines of JavaScript. (Example
included)
 You can create a DNS server.

 You can create a Static File Server.

 You can create a Web Chat Application like GTalk
in the browser.
 Node.js can also be used for creating online
games, collaboration tools or anything which sends
updates to the user in real-time.

EXAMPLE -2 &3 (HTTP SERVER & TCP
SERVER)
 Following code creates an HTTP Server and prints
‘Hello World’ on the browser:
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello Worldn'); }).listen(5000, "127.0.0.1");

 Here is an example of a simple TCP server which
listens on port 6000 and echoes whatever you send
it:
var net = require('net');
net.createServer(function (socket) {
socket.write("Echo serverrn");
socket.pipe(socket); }).listen(6000, "127.0.0.1");

NODE.JS ECOSYSTEM
 Node.js heavily relies on modules, in previous
examples require keyword loaded the http & net
modules.
 Creating a module is easy, just put your JavaScript
code in a separate js file and include it in your code
by using keyword require, like:
var modulex = require(‘./modulex’);
 Libraries in Node.js are called packages and they
can be installed by typing
npm install ‚package_name‛; //package should be
available in npm registry @ nmpjs.org
 NPM (Node Package Manager) comes bundled
with Node.js installation.

EXAMPLE-4: LETS CONNECT TO A DB
(MONGODB)
 Install mongojs using npm, a mongoDB driver for
Node.js
npm install mongojs

 Code to retrieve all the documents from a collection:
var db = require("mongojs")
.connect("localhost:27017/test", ['test']);
db.test.find({}, function(err, posts) {
if( err || !posts) console.log("No posts found");
else posts.forEach( function(post) {
console.log(post);
});
});

WHEN TO USE NODE.JS?
 Node.js is good for creating streaming based real-
time services, web chat applications, static file
servers etc.
 If you need high level concurrency and not worried
about CPU-cycles.
 If you are great at writing JavaScript code because
then you can use the same language at both the
places: server-side and client-side.
 More can be found at:
http://stackoverflow.com/questions/5062614/how-
to-decide-when-to-use-nodejs

EXAMPLE-5: TWITTER STREAMING
 Install nTwitter module using npm:
Npm install ntwitter
 Code:
var twitter = require('ntwitter');
var twit = new twitter({
consumer_key: ‘c_key’,
consumer_secret: ‘c_secret’,
access_token_key: ‘token_key’,
access_token_secret: ‘token_secret’});
twit.stream('statuses/sample', function(stream) {
stream.on('data', function (data) {
console.log(data); });
});

SOME NODE.JS BENCHMARKS
Taken from:
http://code.google.com/p/node-js-vs-apache-
php-benchmark/wiki/Tests
A benchmark between Apache+PHP
and node.js, shows the response
time for 1000 concurrent connections
making 10,000 requests each, for 5
tests.

Taken from:
http://nodejs.org/jsconf2010.pdf
The benchmark shows the
response time in milli-secs
for 4 evented servers.

WHEN TO NOT USE NODE.JS
 When you are doing heavy and CPU intensive
calculations on server side, because event-loops are
CPU hungry.
 Node.js API is still in beta, it keeps on changing a lot
from one revision to another and there is a very little
backward compatibility. Most of the packages are also
unstable. Therefore is not yet production ready.
 Node.js is a no match for enterprise level application
frameworks like
Spring(java), Django(python), Symfony(php) etc.
Applications written on such platforms are meant to be
highly user interactive and involve complex business
logic.
 Read further on disadvantages of Node.js on Quora:
http://www.quora.com/What-are-the-disadvantages-of-

APPENDIX-1: WHO IS USING NODE.JS IN
PRODUCTION?

 Yahoo! : iPad App Livestand uses Yahoo!
Manhattan framework which is based on Node.js.
 LinkedIn : LinkedIn uses a combination of Node.js
and MongoDB for its mobile platform. iOS and
Android apps are based on it.
 eBay : Uses Node.js along with ql.io to help
application developers in improving eBay’s end
user experience.
 Dow Jones : The WSJ Social front-end is written
completely in Node.js, using Express.js, and many
other modules.
 Complete list can be found at:
https://github.com/joyent/node/wiki/Projects,-
Applications,-and-Companies-Using-Node

APPENDIX-2: RESOURCE TO GET STARTED
 Watch this video at Youtube:
http://www.youtube.com/watch?v=jo_B4LTHi3I
 Read the free O’reilly Book ‘Up and Running with
Node.js’ @
http://ofps.oreilly.com/titles/9781449398583/
 Visit www.nodejs.org for Info/News about Node.js

 Watch Node.js tutorials @ http://nodetuts.com/

 For Info on MongoDB:
http://www.mongodb.org/display/DOCS/Home
 For anything else Google!

APPENDIX-3: SOME GOOD MODULES
 Express – to make things simpler e.g. syntax, DB
connections.
 Jade – HTML template system

 Socket.IO – to create real-time apps

 Nodemon – to monitor Node.js and push change
automatically
 CoffeeScript – for easier JavaScript development

 Find out more about some widely used Node.js
modules at: http://blog.nodejitsu.com/top-node-
module-creators

Introduction to Node.js

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