Node JS Introduction

Node.js is an open-source, server-side JavaScript runtime environment built on the V8 JavaScript engine. It allows developers to execute JavaScript code on the server-side, outside of a web browser. 

A Node.js app runs in a single process, without creating a new thread for every request. Node.js provides a set of asynchronous I/O primitives in its standard library that prevent JavaScript code from blocking and generally, libraries in Node.js are written using non-blocking paradigms, making blocking behavior the exception rather than the norm.

When Node.js performs an I/O operation, like reading from the network, accessing a database or the filesystem, instead of blocking the thread and wasting CPU cycles waiting, Node.js will resume the operations when the response comes back.

This allows Node.js to handle thousands of concurrent connections with a single server without introducing the burden of managing thread concurrency, which could be a significant source of bugs.

Now, install node js on your machine/desktop/laptop

1. Visit the official Node.js website: https://nodejs.org
2. On the Node.js website, you'll see two versions available: LTS (Long-Term Support) and Current. It's recommended to choose the LTS version for stability unless you have specific reasons to use the Current version.
3. Click on the LTS download button to download the Node.js installer for your operating system. Node.js is available for Windows, macOS, and Linux.
4. Once the installer is downloaded, run it on your computer. The installation process may vary slightly depending on your operating system.
5. After the installation is complete, you can verify that Node.js is installed by opening a terminal or command prompt and running the following command: node -v

PS F:\NODEJS\nest-excercise> node -v

v18.15.0

Ready to run your first nodejs server 

create a new source file in the any desired folder and call it index.js.

Open index.js in any preferred text editor and paste in the following content:

const http = require('node:http');

const hostname = '127.0.0.1';

const port = 3000;

const server = http.createServer((req, res) => {

  res.statusCode = 200;

  res.setHeader('Content-Type', 'text/plain');

  res.end('Hello, World!\n');

});

server.listen(port, hostname, () => {

  console.log(`Server running at http://${hostname}:${port}/`);

});

Save the file, go back to the terminal window (terminal should be opened in the created folder), and enter the following command:

$ node index.js

Output like this should appear in the terminal:

Server running at http://127.0.0.1:3000/

Now, open any preferred web browser and visit http://127.0.0.1:3000.

If the browser displays the string Hello, World!, that indicates the server is working.