Node.js How to Convert Buffer to String Easily

In Node.js, convert a Buffer to a string by calling buffer.toString(), optionally passing the encoding like buffer.toString('utf8').

Examples

InputBuffer.from('Hello')

OutputHello

InputBuffer.from([72, 101, 108, 108, 111])

OutputHello

InputBuffer.from('48656c6c6f', 'hex')

OutputHello

How to Think About It

To convert a Buffer to a string, think of the Buffer as a container holding bytes. You use the Buffer's built-in toString() method to translate those bytes into readable text, specifying the encoding if needed.

Algorithm

1

Get the Buffer object you want to convert.

2

Call the <code>toString()</code> method on the Buffer.

3

Optionally, pass the encoding type like 'utf8' to <code>toString()</code>.

4

Return the resulting string.

Code

nodejs

const buffer = Buffer.from('Hello, world!');
const str = buffer.toString('utf8');
console.log(str);

Output

Hello, world!

Dry Run

Let's trace converting Buffer.from('Hello') to string.

1

Create Buffer

buffer =

2

Call toString()

buffer.toString('utf8') returns 'Hello'

3

Print result

Output is 'Hello'

Step	Buffer Content	String Result
1
2		Hello
3		Hello

Why This Works

Step 1: Buffer holds bytes

A Buffer stores raw bytes, which are not human-readable text.

Step 2: toString() converts bytes

The toString() method reads the bytes and converts them into a string using the specified encoding.

Step 3: Encoding matters

Using the correct encoding like utf8 ensures the bytes map correctly to readable characters.

Alternative Approaches

Using TextDecoder

nodejs

const { TextDecoder } = require('util');
const decoder = new TextDecoder('utf8');
const buffer = Buffer.from('Hello');
console.log(decoder.decode(buffer));

TextDecoder is a modern API that can decode buffers with more control but requires importing from 'util'.

Buffer to JSON then stringify

nodejs

const buffer = Buffer.from('Hello');
const json = buffer.toJSON();
const str = String.fromCharCode(...json.data);
console.log(str);

This method converts buffer to JSON and then to string but is less efficient and more complex.

Complexity: O(n) time, O(n) space

Time Complexity

Converting a Buffer to string requires reading each byte once, so it is O(n) where n is the buffer length.

Space Complexity

The output string requires space proportional to the buffer size, so O(n) extra space.

Which Approach is Fastest?

Using buffer.toString() is the fastest and simplest method; alternatives add overhead or complexity.

Approach	Time	Space	Best For
buffer.toString()	O(n)	O(n)	Simple and fast conversion
TextDecoder.decode()	O(n)	O(n)	More control over decoding
Buffer to JSON then String.fromCharCode	O(n)	O(n)	Rarely used, less efficient