nodejs vatsal shah

NODE JS INTRODUCTION

Vatsal Shah

Software Embedded Engineer

Deeps Technology

www.vatsalshah.in

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!)

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Vatsal Shah | Node Js

Why node.js ?

Non Blocking I/O

V8 Java script Engine

Single Thread with Event Loop

40,025 modules

Windows, Linux, Mac

1 Language for Frontend and Backend

Active community

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Why node.js ?

Build Fast! JS on server and client allows for more code reuse

A lite stack (quick create-test cycle)

Large number of offerings for web app creation

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Why node.js ?

JS across stack allows easier refactoring

Smaller codebase

See #1 (Build Fast!)

Adapt Fast!

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Why node.js ?

Run Fast! Fast V8 Engine

Great I/O performance with event loop!

Small number of layers

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Why node.js use event-based?

In a normal process cycle the web server while processing the request will have to wait for the IO operations and thus blocking the next request to be processed.

Node.JS process each request as events, The server doesn’t wait for the IO operation to complete while it can handle other request at the same time.

When the IO operation of first request is completed it will call-back the server to complete the request.

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HTTP Method

GET

POST

PUT

DELETE

GET => Read

POST => Create

PUT => Update

DELETE => Delete

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Node.js Event Loop

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There are a couple of implications of this apparently very simple and basic model • Avoid synchronous code at all costs because it blocks the event loop • Which means: callbacks, callbacks, and more callbacks

Blocking vs. Non-Blocking

Example :: Read data from file and show data

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Blocking

Read data from file

Show data

Do other tasks

var data = fs.readFileSync( “test.txt” );

console.log( data );

console.log( “Do other tasks” );

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Non-Blocking

Read data from file

When read data completed, show data

Do other tasks

fs.readFile( “test.txt”, function( err, data ) {

console.log(data);

});

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Node.js Modules

https://npmjs.org/

# of modules = 1,21,943

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https://npmjs.org/

Modules

$npm install <module name>

Modules allow Node to be extended (act as libaries)

We can include a module with the global require function, require(‘module’)

Node provides core modules that can be included by their name:

File System – require(‘fs’)

Http – require(‘http’)

Utilities – require(‘util’)

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Modules

We can also break our application up into modules and require them using a file path:

‘/’ (absolute path), ‘./’ and ‘../’ (relative to calling file)

Any valid type can be exported from a module by assigning it to module.exports

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NPM Versions

Var Versions (version [Major].[Minor].[Patch]):

= (default), >, <, >=, <=

* most recent version

1.2.3 – 2.3.4 version greater than 1.2.3 and less than 2.3.4

~1.2.3 most recent patch version greater than or equal to 1.2.3 (>=1.2.3 <1.3.0)

^1.2.3 most recent minor version greater than or equal to 1.2.3 (>=1.2.3 <2.0.0)

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NPM Commands

Common npm commands:

npm init initialize a package.json file

npm install <package name> -g install a package, if –g option is given package will be installed as a global, --save and --save-dev will add package to your dependencies

npm install install packages listed in package.json

npm ls –g listed local packages (without –g) or global packages (with –g)

npm update <package name> update a package

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File package.json First, we need to create a package.json file for our app

Contains metadata for our app and lists the dependencies

Package.json Interactive Guide

Project informations Name Version Dépendances Licence Main file Etc...

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http://browsenpm.org/package.json



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

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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.

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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 World\n'); }).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 server\r\n");

socket.pipe(socket); }).listen(6000, "127.0.0.1");

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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);

});

});

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When to use it ? Chat/Messaging Real-time Applications High Concurrency Applications Coordinators Web application Streaming server Fast file upload client Any Real-time data apps Anything with high I/O

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Who is using Node.js in production?

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Getting Started

http://nodejs.org/ and Download tar.gz

Extract to any directory

$ ./configure && make install

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http://nodejs.org/

Thank You