Buffers in Node.js

Buffers handle raw binary data. Think of them as arrays of bytes.

Creating Buffers

const buf1 = Buffer.from('Hello World');
console.log(buf1);

const buf2 = Buffer.alloc(10);

const buf3 = Buffer.from([72, 101, 108, 108, 111]);
console.log(buf3.toString());

Output:

<Buffer 48 65 6c 6c 6f 20 57 6f 72 6c 64>
Hello

Encoding Conversions

const text = 'Hello World';
const buf = Buffer.from(text, 'utf8');

const base64 = buf.toString('base64');
console.log(base64);

const decoded = Buffer.from(base64, 'base64').toString('utf8');
console.log(decoded);

Output:

SGVsbG8gV29ybGQ=
Hello World

Real Example: Image to Base64

const fs = require('fs');

const imageBuffer = fs.readFileSync('photo.jpg');

const base64Image = imageBuffer.toString('base64');

const dataURI = `data:image/jpeg;base64,${base64Image}`;

console.log(dataURI);

Use this to embed images in HTML or send via API.

Real Example: Check File Type

const fs = require('fs');

const buffer = fs.readFileSync('unknown-file');

if (buffer[0] === 0xFF && buffer[1] === 0xD8) {
  console.log('This is a JPEG file');
} else if (buffer[0] === 0x89 && buffer[1] === 0x50) {
  console.log('This is a PNG file');
} else if (buffer[0] === 0x47 && buffer[1] === 0x49) {
  console.log('This is a GIF file');
}

Every file type has a unique signature (magic bytes).

Buffer Operations

const buf = Buffer.from('Hello');

console.log(buf.length);

console.log(buf[0]);

buf[0] = 74;
console.log(buf.toString());

const slice = buf.slice(0, 2);
console.log(slice.toString());

Output:

5
72
Jello
Je

Concatenate Buffers

const buf1 = Buffer.from('Hello ');
const buf2 = Buffer.from('World');

const combined = Buffer.concat([buf1, buf2]);
console.log(combined.toString());

Output: Hello World

Real Example: File Upload

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

const upload = multer({ storage: multer.memoryStorage() });

app.post('/upload', upload.single('file'), (req, res) => {
  const buffer = req.file.buffer;
  
  const base64 = buffer.toString('base64');
  
  res.json({
    filename: req.file.originalname,
    size: buffer.length,
    base64: base64.substring(0, 100) + '...'
  });
});

app.listen(3000);

Key Takeaway

Buffers handle binary data like images, files, and network packets. Use Buffer.from() to create, toString() to convert. Essential for file operations and working with binary protocols.