Buffer class in Node.js

Wander into Node.js built-in class Buffer and explore the world of binary data, and play around the equivalent conversion between hexadecimal, decimal, plus other characters at easy level.

💻 01001001 01010101

Introduction

Binary

Get to know about binary data.

• Computers actually work on ones 1 and zeroes 0.
• A single state represents 1 bit (e.g. 0 or 1).
• 1 byte is equal to 8 bits (e.g. 01001001)
• A single character is equal to 1 byte.

Counting in Binary

Decimal	Binary
0	0
1	1
2	10
3	11
4	100
5	101

This table shows a decimal value and its equivalent in binary.

Check this section to check how to convert decimal to binary using Node.js.
Check this blog post to check how to manually convert decimal to binary or "bitwise"

Character System

System	Base	Characters
Binary	2	0 1
Decimal	10	0 1 2 3 4 5 6 7 8 9
Hexadecimal	16	0 1 2 3 4 5 6 7 8 9 a b c d e f

Buffer

Apply and experiment on it using Node.js built-in Buffer class.

Code along

Better learning comes when you're doing hands-on experience

1. Prerequisite: Node.js installed (v20+ is recommended)
2. Create index.mjs file. (Rename it anyway you want)
3. Execute the file via command: node index.mjs

import { Buffer } from 'node:buffer'; // (1)

const buffer = Buffer.from('IU', 'utf-8'); // (2)

console.log(buffer);
// Output: <Buffer 49 55>

1. This may be optional when Node.js export Buffer as global
2. When encoding is not specified, it will default to utf-8

String to Buffer

• <Buffer ...>: indicates that the following hexadecimal values represent a buffer.
• 49 55: These hexadecimal values represent the content of the buffer. Each pair corresponds to a single byte.

Hexadecimal to Decimal

const hex = 16; // (1)!
console.log(parseInt('49', hex)); // 73
console.log(parseInt('55', hex)); // 85

1. Remember that hexadecimal is base16. Review this section

The parseInt(string, radix?) will convert the string to integer which we can use to get its equivalent ASCII character.

Decimal to Character

console.log(String.fromCharCode(73)); // I
console.log(String.fromCharCode(85)); // U

Use loop as a better alternative:

const buffer = Buffer.from('IU', 'utf-8');

buffer.forEach((byte) => {
  console.log(String.fromCharCode(byte));
}); // (1)!

// Output:
// I
// U

1. This also works:

   for (const byte of buffer) {
     console.log(String.fromCharCode(byte));
   }
   

When using loop, each iteration contains a decimal value instead.

While <Buffer ...> contains hexadecimal values, and NOT decimal.

Decimal to Binary

const buffer = Buffer.from('IU', 'utf-8');

buffer.forEach((byte) => {
  console.log(byte.toString(2)); // 2 = base2 or binary
});

// Output:
// 1001001
// 1010101

More examples using this counting in binary table above.

const numbers = [0, 1, 2, 3, 4, 5];

numbers.forEach((n) => {
  console.log(n.toString(2));
});

// Output:
// 0
// 1
// 10
// 11
// 100
// 101

Buffer to String

console.log(buffer.toString()); // defaults to 'utf-8'
console.log(buffer.toString('utf-8'));

// Output:
// IU
// IU

TextEncoder and TextDecoder

TextEncoder and TextDecoder have a method called encode and decode, respectively, that both returns Uint8Array which is the closest equivalent to Buffer.

See reference

new TextEncoder().encode('IU'); // Uint8Array(2) [ 73, 85 ]

Buffer.from([73, 85]).toString(); // IU
new TextDecoder().decode(new Uint8Array([73, 85])); // IU

Tip

Since Node.js Buffer is not available in web or client-side, then you can use this alternative.

Also, TextEncoder and TextDecoder is available in Node.js as well.

Conclusion

There you have learned the equivalent and conversion of data between binary, decimal, hexadecimal and alphabet characters using Buffer class built-in from Node.js.

System	Value
Characters	IU
Hexadecimal	49 55
Binary	1001001 1010101
Decimal	73 85

You can also use Buffer to convert your characters to base64

const buffer = Buffer.from('IU', 'utf-8');

console.log(buffer.toString('base64'));
// SVU=

console.log(Buffer.from('SVU=', 'base64').toString());
// IU

In browser, the equivalent is using:

window.btoa('IU');
// SVU=

window.atob('SVU=');
// IU

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This is just the basics of using Buffer, but there is much more to it.

Buffer is particularly useful when dealing with binary protocols, such as reading and writing files, network communications, cryptographic operations, and other scenarios where handling binary data is necessary.

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