n this tutorial, we will learn about Express.js, Install Express via the Node Package Manager and Create Sample Web server using express.js.

1. ndjidoardo.bar@hypercube-research.com

2. JavaScriptcreatedin1995byBrendanEich(@Netscapelabs).
JS become a ECMA (European Computer Manufacturers
Association)standardby1997.Itremainsastandardinclient- side
appoveryears.
GoogleV8,chrome,Sep2008
Nodecreatedin 2009byRyanDahlusingV8power(c++&
javascript):WithNodeJSstartbeingasaserver-sidelanguage.

3. Highlyscalablewebserversforwebapplications.
Webservices(RESTfulAPI)
Real-TimeappsasitssupportsWeb-Sockets.
Appwithqueuedinputs.
Datastreamingapps.

5. Single-threadedexecutionwiththeuseofcallbackfunctions=>notresource-
intensive
◦ suitableforhighlatencyI/Ooperationse.g:databaseaccess
◦ ScalableasitcombinesServerandapplicationlogicinonesingleplace

6. Nodeisevent-driven,ithandlesallrequestsasynchronouslyfromonsingle
thread.
Aeventloopisusedtoscheduletasksintheevent-drivenprogramming.
NodeprogrammingstyleischristenedContinous-PassingStyle(CPS):Every
asynchronousfunctionhasatleastaCallbackfunctionasoneofitsparameters.This
lateriscallaftertheasynchronoussectionisexecuted.
var fs = require("fs");
fs.readFile ("foo.txt", "utf8", function(error,
data) {
if (error) {
throw error;
}
console.log(data);
});
console.log("Reading file...");

7. Using async module
Using process.nextTick() trick:
function add (x, y, callback) {
setTimeout(function() {
callback(x + y);
},0);
}
add(2, 3, console.log);
console.log("The sum is:" );
function add (x, y, callback) {
process.nextTick(function() {
callback(x + y);
});
}
add(2, 3, console.log);
console.log("The sum is:" );

8. Non-blocking has always to do with I/O (file system,
database,…)
The following code is asyn but not Non-blocking:
function add (x, y, callback) {
process.nextTick(function() {
while (1) {
callback(x + y);
}
});
}
add(2, 3, console.log);
console.log("The sum is:" );

9. Install NodeJS :
http://nodejs.org/download/

10. Create a app.js file with the following code:
Start your server by issuing the following cmd:
◦ > node app.js
Nb: NodeJS has got a REPL!

11. NodeJS extensions are known as modules
NodeJS is being backed by an active community which provides
an overwhelming number of modules
NPM command is used to install and manage new modules:
◦ Ex:
npm install async
npm install async@1.0.x
npm install –g async
npm serach <MODULE_NAME>
npm outdated
npm update npm –g
npm rm asyn
« require(<MODULE_NAME>)» is used to load a given module

12. ExpressJS helps to fit web projects to MCV design pattern
To install ExpressJS:
◦ > npm install –g express
Express has got a scafolding capability that help you create a sustainable
project structure, easy to extend and maintain. Express-generator is the
module dedicated to that job.
◦ > npm install –g express-generator

13. Find a ExpressJS app example on my GITHUB:
◦ https://github.com/ndjido/NodeJS_intro