introduction to node.js

INTRODUCTION TO NODE.JS

Md Sohel Rana

About MeMd. Sohel RanaFounder, NerdDevshttp://www.nerddevs.comtwitter : @sohel023010skype : sohel023010https://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 filevar fs = require('fs')

fs.readFile('/etc/hosts', 'utf8', function (err, data) { if (err) { return console.log(err); } console.log(data);});

Callback

Web ServerAn http server : var http = require('http');

http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello World\n');}).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_name’)

Reusability

Node ModulesA 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 MongoDBvar 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);});

Express web app

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 Examplesapp.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

Who are using

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

Question?