Question

I know that node.js is said to be “event-driven I/O” server-side javascript hosted on V8 Javascript engine. I visited the node.js website, and then read the wikipedia entry, but cant quite get the whole idea of where to use it and how it will be useful. “Event-driven I-O”? “V8 Javascript engine”? In some context though, I see that using “server-side” javascript as a little overkill..I take for instance this piece of code in the wikipedia entry of node.js:

var http = require('http');

http.createServer(function (request, response) {
    response.writeHead(200, {'Content-Type': 'text/plain'});
    response.end('Hello World\n');
}).listen(8000);

console.log('Server running at http://127.0.0.1:8000/');

I have been thinking, is there really a significant purpose in running a server that particularly serves javascript files that are executed in the front-end part of the application?

I also forked the node.js repo in github to learn more about how it works, and it turns out that some of its modules are written in C++. So it is not a javascript after all then?

Can somebody give me a clear explanation about all this? Sorry if the question is not clear or something, I am just a beginner. Will appreciate any input/suggestions. thanks

Answer 1

The node.js server is, in simple terms, a replacement for something like the Apache web server – but it is largely written in JavaScript which runs on the server (executed by the V8 engine) rather than on the client side. It can be extended with ‘native code’ modules (written in e.g. C++) wrapped in a JavaScript interface to add functionality, but AFAIK most node.js modules are pure JavaScript.

“Event driven I/O” is just a term that describes the normal asynchronous callback mechanisms you’re used to in JavaScript. In node.js you supply callbacks for all sorts of things, and your function is called when the relevant event occurs.

Depending on how many modules you add, a node.js server is relatively lightweight compared to something like Apache, and in some ways a lot simpler.

The two main advantages to node.js I see are:

1. It allows you to write both the server-side and client-side parts of a web application in the same language. In some cases you can use the same code on both sides.
2. It makes server-side coding accessible to all those web developers out there that know JavaScript without having to learn a more common server-side language like PHP or Java.

Here’s an article I just came across that might also shed some light: What is Node.js?