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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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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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 Worldn'); }).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 serverrn");
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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