Buffer Class in Node.js

What is Buffer?

Buffer is a class that provides a way to work with binary data directly. It’s used to handle streams of binary data, such as reading files or network communications.

Creating Buffers

// From string
const buf1 = Buffer.from('Hello');

// From array
const buf2 = Buffer.from([72, 101, 108, 108, 111]);

// Allocate buffer
const buf3 = Buffer.alloc(10); // 10 bytes, filled with 0
const buf4 = Buffer.allocUnsafe(10); // Faster, not initialized

// From buffer
const buf5 = Buffer.from(buf1);

Buffer Methods

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

// Length
console.log(buf.length); // 11

// Convert to string
console.log(buf.toString()); // 'Hello World'
console.log(buf.toString('hex')); // Hexadecimal
console.log(buf.toString('base64')); // Base64

// Write to buffer
buf.write('Hi');
console.log(buf.toString()); // 'Hi World'

// Compare buffers
const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('ABC');
console.log(buf1.equals(buf2)); // true

// Concatenate
const buf3 = Buffer.concat([buf1, buf2]);

Working with Binary Data

const buf = Buffer.alloc(4);

// Write integers
buf.writeInt8(127, 0);
buf.writeInt16BE(1000, 1);

// Read integers
console.log(buf.readInt8(0)); // 127
console.log(buf.readInt16BE(1)); // 1000

File Operations

const fs = require('fs');

// Read file as buffer
fs.readFile('image.png', (err, buffer) => {
  console.log(buffer); // <Buffer ...>
  console.log(buffer.length);
});

// Write buffer to file
const data = Buffer.from('Hello World');
fs.writeFile('output.txt', data, (err) => {
  if (err) throw err;
  console.log('File written');
});

Encoding

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

// Different encodings
console.log(buf.toString('utf8')); // Hello
console.log(buf.toString('hex')); // 48656c6c6f
console.log(buf.toString('base64')); // SGVsbG8=
console.log(buf.toString('ascii')); // Hello

Buffer and Streams

const fs = require('fs');

const readStream = fs.createReadStream('large-file.txt');

readStream.on('data', (chunk) => {
  console.log('Chunk:', chunk); // Buffer
  console.log('Size:', chunk.length);
});

Interview Tips

• Explain Buffer purpose: Handle binary data
• Show creation methods: from, alloc, allocUnsafe
• Demonstrate conversions: toString, different encodings
• Mention use cases: Files, streams, network data
• Discuss performance: allocUnsafe vs alloc

Summary

Buffer is a Node.js class for handling binary data. Create with Buffer.from(), Buffer.alloc(), or Buffer.allocUnsafe(). Convert to strings with toString(). Used extensively with files, streams, and network operations.