Node.js — File System

Import fs Module

const fs = require('fs');
const fsPromises = require('fs').promises;

Reading Files

// Synchronous
const data = fs.readFileSync('file.txt', 'utf8');
console.log(data);

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

// Promise-based
const data = await fsPromises.readFile('file.txt', 'utf8');

Writing Files

// Synchronous
fs.writeFileSync('output.txt', 'Hello, World!');

// Asynchronous
fs.writeFile('output.txt', 'Hello', (err) => {
    if (err) throw err;
    console.log('File written');
});

// Promise-based
await fsPromises.writeFile('output.txt', 'Hello');

Append to Files

fs.appendFileSync('log.txt', 'New line\n');
await fsPromises.appendFile('log.txt', 'New line\n');

File Operations

// Check if file exists
if (fs.existsSync('file.txt')) { ... }

// Delete file
fs.unlinkSync('file.txt');

// Rename file
fs.renameSync('old.txt', 'new.txt');

// Get file stats
const stats = fs.statSync('file.txt');
console.log(stats.size, stats.mtime);

Directory Operations

// Create directory
fs.mkdirSync('new-dir', { recursive: true });

// Read directory
const files = fs.readdirSync('.');

// Remove directory
fs.rmdirSync('dir');

Mini Practice

1. Read a file
2. Write to a file
3. Append content
4. List directory contents

Up Next

Continue with Path — working with file paths.