SEENUVASAN P

Posted on Jun 18

Day 15: Getting Started with Node.js: My First Day Journey

#node #payilagam

Today, I started learning Node.js, and I’m excited to share the basics I explored—like creating a server, using built-in modules, and understanding how Node.js works under the hood.

What is Node.js?

Node.js is a runtime environment that allows you to run JavaScript on the server-side. It's built on the Chrome V8 JavaScript engine, which makes it fast and efficient.

Creating a Simple Server

const http = require('http');

const server = http.createServer((req, res) => {
  res.write('Hello World!');
  res.end();
});

server.listen(3000, () => {
  console.log('Server is running on http://localhost:3000');
});

This code sets up a basic web server that listens on port 3000.

Sending a Request

You can test this using your browser or a tool like curl:

curl http://localhost:3000

Importing Node.js Core Modules

Here are some useful built-in modules:

const fs = require('fs');       // File system
const path = require('path');   // File path handling
const os = require('os');       // OS info
const https = require('https'); // HTTPS requests

Example: Reading a file using fs

fs.readFile('example.txt', 'utf8', (err, data) => {
if (err) throw err;
console.log(data);
});

Synchronous vs Asynchronous

Synchronous code blocks execution:

const data = fs.readFileSync('example.txt', 'utf8');
console.log(data); // waits for the file to be read

Asynchronous code doesn't block:

fs.readFile('example.txt', 'utf8', (err, data) => {
  console.log(data); // executed later
});

Callbacks

Callback example:

function greet(name, callback) {
  console.log('Hello, ' + name);
  callback();
}

greet('Alice', () => {
  console.log('Callback executed');
});

Streams (Reading/Writing Data in Chunks)

const readStream = fs.createReadStream('largefile.txt', 'utf8');

readStream.on('data', chunk => {
  console.log('Chunk received:', chunk);
});

Streams help with performance when handling large files.

Summary of Concepts I Learned

Node.js runs JavaScript outside the browser

Created a server with the http module

Imported built-in modules: fs, path, os, https

Understood sync vs async

Explored callbacks, promises, and async/await

Learned about the event loop and single-threaded architecture

Used streams for handling large data

What’s Next?

Next, I plan to learn:

Express.js (web framework)

Building REST APIs

Handling JSON and databases (like MongoDB)

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