18_Node.js.ppt

Introduction to Node.js®
Jitendra Kumar Patel
Saturday, January 31, 2015

Why node.js ?
“Node's goal is to provide an easy way to build
scalable Network programs”

• Created by Ryan Dahl in 2009
• Development && maintenance sponsored by Joyent
• Licence MIT
• Last release : 0.10.31
• Based on Google V8 Engine
• +99 000 packages
About Node.js……

● Vert.x => Polygot programming
● Akka => Scala and Java
● Tornado => Python
● Libevent => C
● EventMachine => Ruby
Other projects like Node.js….

● Another Web framework
● For beginner
● Multi-thread
Node.js is not……

• Traditional desktop applications have a user interface wired up with
background logic
– user interfaces are based on Windows Forms, Jswing, WPF, Gtk, Qt, etc.
and dependant on operating system
• On the web user interfaces are standardized
– HTML for markup
– CSS for style
– JavaScript for dynamic content
• In the past proprietary technologies existed on the web, e.g. Adobe
Flash, ActiveX
– They are slowly dying
• Data is generated on the server, transferred to the client and displayed
by the browser
• Server Side technologies include PHP, JSP, ASP.net, Rails, Djanog, and
yes, also node.js
Development for the Web….

● REST = REpresentational State Transfer
● Not new technology
● Architectural style for client-server
REST……

● General interface
● Scalability of component interface
● Reduce latency
● Encapsulate legacy system
Goals of REST……..

● GET
● POST
● PUT
● DELETE
HTTP Method……

● POST => Create
● GET => Read
● PUT => Update
● DELETE => Delete
HTTP Method with CRUD…..

● Non Blocking I/O
● V8 Javascript Engine
● Single Thread with Event Loop
● 40,025 modules
● Windows, Linux, Mac
● 1 Language for Frontend and Backend
● Active community
Why node.js ?

• Asynchronous i/o framework
• Core in c++ on top of v8
• Rest of it in javascript
• Swiss army knife for network Related stuffs
• Can handle thousands of Concurrent connections with
Minimal overhead (cpu/memory) on a single process
• It’s NOT a web framework, and it’s also NOT a language
What is node.js?
« A platform built on
Chrome's JavaScript runtime
for easily building fast,
scalable network
applications. »
http://nodejs.org/

• Friendly callbacks
• Ubiquitous
• No I/o Primitives
• One language to RULE them all
JavaScript is well known for client-side scripts running inside the browser
node.js is JavaScript running on the server-side
SSJS -> Server-Side JavaScript
Use a language you know
Use the same language for client side and server side
Why javascript ?!!!

• Perform asynchronous processing on single thread instead of classical
multithread processing, minimize overhead & latency, maximize scalability
• Scale horizontally instead of vertically
• Ideal for applications that serve a lot of requests but dont use/need lots of
computational power per request
• Not so ideal for heavy calculations, e.g. massive parallel computing
• Also: Less problems with concurrency
The idea behind node.js….

Node.js Event Loop
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

Example :: Read data from file and show data
Blocking vs Non-Blocking……

● Read data from file
● Show data
● Do other tasks
var data = fs.readFileSync( “test.txt” );
console.log( data );
console.log( “Do other tasks” );
Blocking…..

● Read data from file
When read data completed, show data
● Do other tasks
fs.readFile( “test.txt”, function( err, data ) {
console.log(data);
});
Non-Blocking…… Callback

• Chat/Messaging
• Real-time Applications
• Intelligent Proxies
• High Concurrency Applications
• Communication Hubs
• Coordinators
When to use it ?

● Web application
● Websocket server
● Ad server
● Proxy server
● Streaming server
● Fast file upload client
● Any Real-time data apps
● Anything with high I/O
Node.js for….

• http://nodejs.org/ and Download tar.gz
• Extract to any directory
• $ ./configure && make install
Getting Started…..

Project informations
• Name
• Version
• Dependencies
• Licence
• Main file
Etc...
File package.json…..

● https://npmjs.org/
● # of modules = 1,21,943
Node.js Modules…..

$npm install <module name>
Install module…..

• var http = require(‘http’);
• var fs = require(‘fs’);
• var express = require(‘express’);
Using module…..

18_Node.js.ppt

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