🗂️ 3.8 Working with File Systems in Node.js — Reading, Writing & Uploading Files Made Easy

Hey there, lil’ coder! 👋

Ever wanted your Node.js app to read from or write to a file? Or maybe let users upload images and documents?

That’s exactly what we’ll learn today! 😎
We’ll use simple language, fun code, and real examples — just like I’m teaching my younger cousin 💡

📦 What Is the File System in Node.js?

Every computer has a file system — a way to organize and manage files and folders.

Node.js gives us a cool tool to play with files: the fs module (short for File System).

This module lets us:

✅ Read files
✅ Write files
✅ Update files
✅ Delete files
✅ And even upload files from users!

📚 How to Use the fs Module in Node.js

Let’s get started by creating a Node.js project:

bashCopyEditmkdir file-system-app
cd file-system-app
npm init -y

Create a file:

bashCopyEdittouch index.js

Now, inside index.js, we’ll start using the built-in fs module.

jsCopyEditconst fs = require('fs');

🎉 That’s it! Now we can start reading and writing files.

📖 1. Reading Files in Node.js

There are 2 ways to read files:

🔄 Synchronous (Blocking) – fs.readFileSync

jsCopyEditconst data = fs.readFileSync('example.txt', 'utf-8');
console.log(data);

• This stops the program until the file is read.
• Use it for small scripts.

🔁 Asynchronous (Non-blocking) – fs.readFile

jsCopyEditfs.readFile('example.txt', 'utf-8', (err, data) => {
  if (err) return console.error(err);
  console.log(data);
});

• Doesn’t block the rest of your app.
• Best for web servers or large files.

📦 Let’s Create a Test File

Create a file called example.txt:

perlCopyEditThis is my first file read in Node.js 🚀

Now run your script. You’ll see the message in your terminal!

🧠 Tip: Always use async methods in real apps. They’re faster and safer!

✍️ 2. Writing Files in Node.js

You can create or replace a file using fs.writeFile:

jsCopyEditfs.writeFile('newFile.txt', 'Hello from Web Codder! 🧡', (err) => {
  if (err) throw err;
  console.log('✅ File written successfully!');
});

• If the file doesn’t exist, Node creates it.
• If it exists, the content gets replaced.

➕ 3. Appending Data to a File

Want to add more data to an existing file? Use fs.appendFile:

jsCopyEditfs.appendFile('newFile.txt', '\nAnother line from Web Codder 🔥', (err) => {
  if (err) throw err;
  console.log('✅ Data appended!');
});

🔍 \n adds a new line between entries.

🧨 4. Deleting a File

Want to remove a file?

jsCopyEditfs.unlink('newFile.txt', (err) => {
  if (err) throw err;
  console.log('🗑️ File deleted!');
});

Be careful — once deleted, it’s gone! 😅

🧺 5. Handling File Uploads with Multer

Now let’s make it fancy 🎩

Imagine your app lets users upload profile pictures.
You’ll need a way to receive and save uploaded files.

Here comes multer — a popular middleware for handling file uploads in Express apps.

📦 Install multer:

bashCopyEditnpm install express multer

🛠️ Basic File Upload Setup

jsCopyEditconst express = require('express');
const multer = require('multer');
const app = express();

const storage = multer.diskStorage({
  destination: (req, file, cb) => cb(null, 'uploads/'),
  filename: (req, file, cb) => cb(null, Date.now() + '-' + file.originalname)
});

const upload = multer({ storage });

app.post('/upload', upload.single('myFile'), (req, res) => {
  res.send('✅ File uploaded successfully!');
});

app.listen(3000, () => console.log('Server running on port 3000'));

📁 Folder Structure After Upload

pgsqlCopyEditfile-system-app/
├── index.js
├── uploads/
│   └── 1715087731873-profile.jpg

🧠 Multer saves your uploaded files to the uploads/ folder.

✅ Recap — What You Learned Today

You’re now a file-system ninja! 🥷

🛠️ Project Ideas to Practice

• 📓 Build a simple Notepad that writes to .txt files
• 📷 Image gallery where users upload and view pictures
• 📂 Backup tool that saves server logs daily

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Let’s keep learning and building together! 💡💻