An Introduction to the world of Javascript and NodeJS. The presentation captures Javascript's history, its evolution and its progression towards a language for an end-to-end development.
Direct Style Effect Systems - The Print[A] Example - A Comprehension Aid
JS & NodeJS - An Introduction
1. 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
2. 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…
3. 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.
11. JS Code – Getting used to
Asynchronous Programming
12. var url = "http://www.google.com";
var someVar = 10;
$.get(url, function(data){
alert("Data Loaded: " + data);
});
JS Code – Some ‘Cool’ Features
- Dynamic types
- Everything is an Object
- Anonymous functions
- Callbacks
- Closures
- No multi-threading
var add = (function () {
var counter = 0;
return function () {return counter
+= 1;}
})();
add();
add();
add();
// the counter is now 3
13. 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
14. 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
15. 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/');
16. 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
17. 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();
18. 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);
19. 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. 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
22. 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!)
