Introduction to node.js

INTRODUCTION TO
NODE.JS
Md Sohel Rana

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

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

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

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

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

 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

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/');

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

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

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>"
}

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

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

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')
;

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

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

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);
});

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

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);
});

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

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
});

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

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

Introduction to node.js

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