Introduction to NodeJS [Simple Explanation]

What is NodeJS?

• An open-source and cross-platform Javascript runtime environment.
• Runs on the Javascript V8 engine (which is the core of Google Chrome)
• Single-threaded and uses asynchronous programming.

If NodeJS is single-threaded, how does it handle multiple requests?

Imagine you go to a restaurant where there is only a single chef. You order Pasta from the waiter. The waiter informs the chef about the order and other customer orders. The chef gets your Pasta order but realizes it will take time to boil your Pasta. Instead of waiting for your Pasta to cook, it keeps it in the stove to boil and meanwhile starts processing the other orders/

NodeJS works similarly.
Chef = Node.js' Main Thread (Node.js can only do one thing at a time on its main thread)

Waiter = Event Loop (The event loop takes incoming requests and decides how to handle them)

Kitchen Helpers = Worker Threads or OS Background Processes (Node.js delegates the work to helpers)

For example, in an I/O operation, when the web server is requested to fetch content from a file, NodeJS simply delegates the work to the OS's file system and gets ready to handle the subsequent request. When the file system responds, it handles that.

Why should I choose NodeJS over other backend applications?

• Same language across the stack: Most front-end development uses JS frameworks like Angular, React, Vue, etc. It would be a massive advantage if the backend application were written in Javascript. Full-stack developers don't need to learn a new language for backend development.

• Ideal for microservice-based architecture: NodeJS's single-threaded event-loop architecture is much more convenient for web developers than multi-threaded architecture, as there is no risk of available threads being finished when handling multiple concurrent requests.

• Fast development: NodeJS is very lightweight, and NodeJS servers can be up and running quickly with little effort.

• NPM: The NodeJS Package Manager is a vast library of code developers write worldwide. It can easily be used as a dependency in a project, shortening the effort to write extra code.

"NodeJS servers can be up and running quickly using little effort" - is it that simple?

YES.

const { createServer } = require('node:http');

const hostname = '127.0.0.1';
const port = 3000;

const server = createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello World');
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

What this code does:

• Uses the http module of NodeJS.
• Configures the host and port.
• Uses the createServer method of http module to create a server.
• Whenever a new request is received, the request event is called, providing two objects: an http.IncomingMessage object and an http.ServerResponse object.
• The created server listens to the host and port.

And that's it. Now, running node server.js, where server.js is the name of your code file, will make your NodeJS server "up and running."