2. JavaScript created in 1995 by Brendan Eich (@Netscape labs) .
JS become a ECMA (European Computer Manufacturers
Association) standard by 1997. It remains a standard in client-
side app over years.
Google V8, chrome, Sep 2008
Node created in 2009 by Ryan Dahl using V8 power (c++ &
javascript) : With Node JS start being as a server-side language.
3. Highly scalable web servers for web applications.
Web services (RESTful API)
Real-Time apps as its supports Web-Sockets.
App with queued inputs.
Data streaming apps.
4.
5. Single-threaded execution with the use of callback functions => not resource-
intensive
◦ suitable for high latency I/O operations e.g: database access
◦ Scalable as it combines Server and application logic in one single place
6. Node is event-driven, it handles all requests asynchronously from on single
thread.
A event loop is used to schedule tasks in the event-driven programming.
Node programming style is christened Continous-Passing Style (CPS): Every
asynchronous function has at least a Callback function as one of its parameters.
This later is call after the asynchronous section is executed.
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:" );
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npm outdated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
