JS & NodeJS - An Introduction

Javascript & NodeJS
An Introduction
“JavaScript is 18...
now it’s not my responsibility;
it can go out, vote, join the Navy,
get drunk and gamble in most states.”
BRENDAN EICH
MOZILLA, 2013

Javascript As we popularly know it
CSS JavaScript
Lay man/Enthusiast ->
- Web comes first to mind
- The (new age) web that is >>
Developers ->
- Develop web page
- Use that calendar widget of Jquery
- Asynchronous updates
Think of JS…

Javascript History
Web in 1995
“We aimed to provide a
“glue language” for the
Web designers and part time
programmers who were
building Web content from
components such as images,
plugins, and Java applets.”
“We saw Java as the
“component language”
used by higher-priced
programmers.”
- Netscape
BRENDAN EICH
An ex Silicon Graphics (7 years) Joined
Netscape in April 1995
prototyped language (Mocha >
LiveScript > JS) and SpiderMonkey
compiler in 10 days in May 1995.

DHTML
FORM VALIDATION
DYNAMIC HTML
Javascript Evolution Web 1995-2K
TICKERS & POP UPSROLLOVERS

Javascript Evolution Web in 2K
XHR
2005
GOOGLE MAPS
2004
GOOGLE MAIL
2000
OUTLOOK WEB
XMLHttpRequest

AJAX
JESSE JAMES GARRETT
ASYNCHRONOUS JAVASCRIPT and XML
Javascript Evolution Web in 2005

Javascript As we popularly know it
CSS JavaScript
How does it work together?

Browser processing pipeline: HTML, CSS, and
JavaScript
Whats happening under the hood?

JS Code – Getting used to
Asynchronous Programming

NodeJS – JS on Server Side
- JS as a language breaks shackles; no longer
associated only with Web
- Runs on v8 engine – wait! Isnt that what Chrome
browser has?
- Event loop architecture…no multi-threading
mess
- Everything is asynchronous

Running node.js
• Download from nodejs.org
• Install with Windows Installer
• apt-get install nodejs on Ubuntu
• Try some commands on the interactive shell
node
> console.log('Hello World');
Hello World

Webserver example
This is the node sample application shown on nodejs.org
and hosts a fully fledged HTTP server, already shows a lot of basic
concepts of nodeJS
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, { 'Content-Type': 'text/plain' });
res.end('Hello Worldn');
}).listen(1337, '127.0.0.1');
console.log('Server running at http://127.0.0.1:1337/');

node.js modules
• developers know libraries, in node.js modules serve a similar function
• put different functionalities in different *.js files and allow usage from
other *.js files
• Helps structuring application
• use exports keyword to expose functions to other modules
• use require keyword to import modules

node.js modules
• create a new file called test.js
• Expose function with exports keyword
• import from main app.js file
exports.helloworld = function () {
console.log('Hello World');
}
var test = require('./test.js');
test.helloworld();

node.js modules
• It is also possible to directly overwrite the exports object with module.exports
• Usually this is done to export the constructor of a JavaScript ‘Class’ and split
class definitions to separate files
module.exports = function () {
this.name = "test object";
this.color = "red";
this.size = "large";
}
var test = require('./test.js');
var testObject = new test();
console.log('name:' + testObject.name);
console.log('color:' + testObject.color);
console.log('size:' + testObject.size);

node.js modules
• apart from self written modules, it is also possible to install
modules from a repository with a package manager
• This package manager is npm
• Similar command syntax to apt
• npm install <module name>
• npm update
• huge amount of public packages (74,753 as of 24th May 2014)
• everyone can contribute

20
structure of a node.js application
You need a *.js file that serves as application entry point
Run it directly with node *.js
package.json

package.json
{
"name": "TestNodejsApp",
"version": "0.0.0",
"description": "TestNodejsApp",
"private": true,
"main": "app.js",
"author": {
"name": "Qiong Wu",
"email": ""
},
"dependencies": {
"express": "3.4.4",
"jade": "*",
"stylus": "*"
}
}

JS – Why I Like it?
1. Dynamically typed -> Freedom with responsibility
2. JSON is de-facto standard & JS knows it best
3. #1 + #2 = flexible/decoupled architecture
4. Saves from mess of multi-threaded world
5. One language for entire stack (wow!)

console.log(“Thank You ”);

JS & NodeJS - An Introduction

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