Buffers in Node.js

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

Creating Buffers

```javascript 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

```javascript 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

```javascript 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

```javascript 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

```javascript 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

```javascript 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

```javascript 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.