How to convert a String to a Byte Array in JavaScript

# How to convert a String to a Byte Array in JavaScript

To convert a string to a byte array in JavaScript:

Instantiate the TextEncoder() constructor to create a TextEncoder object.
Call the encode() method on the object to convert the string to a byte array.

index.js

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const utf8EncodeText = new TextEncoder();

const str = 'bobbyhadz.com';

const byteArray = utf8EncodeText.encode(str);

// Uint8Array(13) [
//    98, 111,  98,  98, 121,
//   104,  97, 100, 122,  46,
//    99, 111, 109
// ]
console.log(byteArray);

convert string to bytearray

The code for this article is available on GitHub

This approach works in the browser and Node.js.

The TextEncoder() constructor creates a TextEncoder object that is used to generate a byte stream with UTF-8 encoding.

The last step is to use the TextEncoder.encode() method.

The method takes a string as a parameter and returns Uint8Array object.

A Uint8Array represents an array of 8-bit unsigned integers.

If you have to convert a string to a byte array often, define a reusable function.

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function strToByteArray(str) {
  return new TextEncoder().encode(str);
}

const byteArray1 = strToByteArray('bobbyhadz.com');
// Uint8Array(13) [
//    98, 111,  98,  98, 121,
//   104,  97, 100, 122,  46,
//    99, 111, 109
// ]
console.log(byteArray1);

The function takes a string as a parameter, converts the string to a byte array and returns the result.

# Decoding the Byte Array back to a string

You can create a TextDecoder object if you need to convert the Byte Array back to a string.

index.js

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const utf8EncodeText = new TextEncoder();

const str = 'bobbyhadz.com';

const byteArray = utf8EncodeText.encode(str);

// Uint8Array(13) [
//    98, 111,  98,  98, 121,
//   104,  97, 100, 122,  46,
//    99, 111, 109
// ]
console.log(byteArray);

const strAgain = new TextDecoder().decode(byteArray);
console.log(strAgain); // 👉️ bobbyhadz.com

decode byte array to string

The code for this article is available on GitHub

We used the TextDecoder() constructor to create a TextDecoder object and called the decode method on the object.

The method takes a buffer (an ArrayBuffer, a TypedArray or a DataView object) and returns a string that contains the text decoded from the buffer.

If you have to decode a byte array often, create a reusable function.

index.js

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// 👇️ converts a string to a byte array
function strToByteArray(str) {
  return new TextEncoder().encode(str);
}

// 👇️ converts a byte array to a string
function byteArrayToStr(buf) {
  return new TextDecoder().decode(buf);
}

const str = 'bobbyhadz.com';

const byteArray = strToByteArray(str);
// Uint8Array(13) [
//    98, 111,  98,  98, 121,
//   104,  97, 100, 122,  46,
//    99, 111, 109
// ]
console.log(byteArray);

const strAgain = byteArrayToStr(byteArray);
console.log(strAgain); // 👉️ bobbyhadz.com

The byteArrayToStr function takes a byte array as a parameter and converts the byte array to a string.

# Using `Buffer.from()` to convert a String to a Byte Array in JavaScript

If you use Node.js, you can also use the Buffer.from method to convert a string to a byte array.

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const str = 'bobbyhadz.com';

const byteArray = Buffer.from(str);

// 👇️ <Buffer 62 6f 62 62 79 68 61 64 7a 2e 63 6f 6d>
console.log(byteArray);

console.log(byteArray.toString()); // 👉️ bobbyhadz.com

convert string to byte array using buffer from

The code for this article is available on GitHub

The method creates a new Buffer that contains the given string.

Note that this approach cannot be used in the browser.

The Buffer.from() method takes a string and an encoding as parameters.

The encoding parameter is optional and defaults to utf8.

Here is an example that explicitly passes the encoding argument.

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const str = 'bobbyhadz.com';

const byteArray = Buffer.from(str, 'utf8');

// 👇️ <Buffer 62 6f 62 62 79 68 61 64 7a 2e 63 6f 6d>
console.log(byteArray);

The encoding parameter sets the character encoding that is used to convert the string to bytes.

If you need to convert the string to a UTF-16 Byte Array, set the encoding to utf16le.

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const str = 'bobbyhadz.com';

const byteArray = Buffer.from(str, 'utf16le');

// 👇️ <Buffer 62 00 6f 00 62 00 62 00 79 00 68 00 61 00 64 00 7a 00 2e 00 63 00 6f 00 6d 00>
console.log(byteArray);

You can use the toString() method if you need to decode the buffer into a string.

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const str = 'bobbyhadz.com';

const byteArray = Buffer.from(str, 'utf16le');

// 👇️ <Buffer 62 00 6f 00 62 00 62 00 79 00 68 00 61 00 64 00 7a 00 2e 00 63 00 6f 00 6d 00>
console.log(byteArray);

console.log(byteArray.toString()); // 👉️ bobbyhadz.com

You can also define a reusable function if you have to convert a string to a byte array often.

index.js

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function strToBytesArray(str, encoding = 'utf8') {
  return Buffer.from(str, encoding);
}

const str = 'bobbyhadz.com';

const byteArray = strToBytesArray(str, 'utf8');

// 👇️ <Buffer 62 6f 62 62 79 68 61 64 7a 2e 63 6f 6d>
console.log(byteArray);

// bobbyhadz.com
console.log(byteArray.toString());

convert string to byte array using reusable function

The code for this article is available on GitHub

The function takes a string and optionally an encoding (defaults to utf8) as parameters and converts the string to a buffer.

I've also written an article on how to convert a JSON object to a Buffer and vice versa in Node.js.

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How to convert a String to a Byte Array in JavaScript