The presentation is an overview of Node.js on how to use it in developing web apps. It also describes the pros and cons it has along with why it got so much adaption in quick time.

1. INTRODUCTION TO
NODE.JS
Md Sohel Rana

2. About Me
Md. Sohel Rana
Founder, NerdDevs
http://www.nerddevs.com
twitter : @sohel023010
skype : sohel023010
https://github.com/sohel-rana

3. What is Node.js
 A runtime
environment to
support JavaScript
as server side
language
 Built on V8-
JavaScript Engine of
Chrome
 Event-driven, non-
blocking I/O

4. Node.js
 Advantages
- Asynchronous I/O, more requests can serve
- JavaScript as a Server Side language
- Event Driven
- A good package manager “NPM”
 Disadvantages
- Single threaded
- Long processing unit can lock down the
whole system
- Not elegant when more levels of callbacks

5. Installation
 Download the package from www.nodejs.org
website and install

6. Hello World!
 Open your favorite text editor and write,
console.log(‘Hello, World!’);
 Save the file as hello_world.js
 In terminal type node hello_world.js and you
should see this output

7.  Node.js is asynchronous
 Every I/O operation needs a callback
//reading host file
var fs = require('fs')
fs.readFile('/etc/hosts', 'utf8', function (err, data) {
if (err) {
return console.log(err);
}
console.log(data);
});
Callback

8. Web Server
An http server :
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello Worldn');
}).listen(9000, '127.0.0.1');
console.log('Server running at http://127.0.0.1:9000/');

9. Node Modules
 A functional unit that
performs specified
actions
 Loaded using
require(‘module_nam
e’)
 Reusability

10. Node Modules
A simple module :
// “modules/calculator.js”
exports.add = function(a, b){
return a+b ;
};
exports.subtract = function(a, b){
return a-b;
};
var Calculator = require('./module/calculator.js');
var addTwoNumber = Calculator.add(5,7);
console.log(addTwoNumber); // will print 12

11. NPM
 NPM- node.js
package manager
 Used to
install/uninstall
node programs
 Can be used to
install
dependencies
 package.json is
used to define
dependencies
//pakage.json
{
"name": "backbone-express-
boilerplate",
"version": "1.0.0",
"scripts": {
"start": "node ./server/bin/www"
},
"dependencies": {
"express": "^4.12.3",
"jade": "~1.9.2”
},
"repository": {
"type": "git",
"url": "https://<repo-url.>git"
},
"author": "Sohel Rana”,
"bugs": {
"url": "https://<repo-url>/issues"
},
"homepage": "https://<repo-
homepage>"
}

12. Supporting Databases
 Has support for
almost every
database
 SQL-Server,
MySQL,
PostgreSQL, Oracle
 Very often used with
MongoDB

13. Connecting with DB
 Install a driver(node_module) for the DB
 Import that module using require
 For MongoDB, we can use Mongoose

14. Connect with MongoDB
var mongoose = require('mongoose');
mongoose.connection.on('open', function (ref) {
console.log('Connected to mongo server.');
//do something here
});
mongoose.connection.on('error', function (err) {
console.log('Could not connect to mongo
server!');
console.log(err);
});
mongoose.connect('mongodb://localhost/mydb')
;

15. Web Frameworks
 NodeJS provides
core modules
 Requires lots of
effort for web apps
 Express, Sails etc.
provides lots of
feature top of it
 Makes the
maintenance easy

16. ExpressJS
 A complete web framework with routing
 Built-in REST API support
 Building API is quick and easy
 For installing, $npm install express --save

17. Express web app
var express = require('express');
var app = express();
app.get('/', function (req, res) {
res.send('Hello World!');
});
var server = app.listen(3000, function () {
var host = server.address().address;
var port = server.address().port;
console.log('Example app listening at http://%s:%s',
host, port);
});

18. Express web app
 Running the app will show this
 If we visit http://localhost:3000 from browser,
we will see

19. Express web app
 Show some html
var express = require('express’);
var app = express();
app.use('/public', express.static('public'));
app.get('/', function (req, res) {
res.sendFile(__dirname + '/index.html');
});
var server = app.listen(3000, function () {
var host = server.address().address;
var port = server.address().port;
console.log('Example app listening at http://%s:%s', host, port);
});

20. Express web app

21. REST API
 An architectural style of building web services
 Uses http verbs GET, POST, PUT, DELETE
 Not a Protocol like SOAP

22. REST API in Express
 app.get(), app.post(), app.put(), app.delete()
 Some Examples
app.get('/user/:id', function(req, res){
res.send('user ' + req.params.id);
});
app.post('/save_user', function (req, res) {
//save user data
});

23. Hosting
 So many Cloud Platforms available
 Nodejitsu, appfog, Heroku, OpenShift
 NodeChef, EvenNode
 Microsoft Azure

24. Who are using

25. Future
 Getting popular for programming in IoT
 IBM, Microsoft investing
 Giant companies are using it
 NodeJS Foundation

26. Question?