Uint8Array - JavaScript | MDN (original) (raw)
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The Uint8Array typed array represents an array of 8-bit unsigned integers. The contents are initialized to 0 unless initialization data is explicitly provided. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
Uint8Array is a subclass of the hidden TypedArray class.
Description
Uint8Array is currently the only TypedArray subclass that has additional methods compared to other typed arrays. Because of its nature as a generic byte array, it is the most suitable for working with arbitrary binary data. It supports two sets of methods for the creation, serialization, and modification of Uint8Array data to/from hex strings and base64 strings.
- Uint8Array.fromBase64(), Uint8Array.prototype.toBase64(), and Uint8Array.prototype.setFromBase64() for working with base64 strings, where 3 bytes are encoded by 4 characters that are either 0–9, A–Z, a–z, "+", and "/" (or "-" and "_", if using URL-safe base64).
- Uint8Array.fromHex(), Uint8Array.prototype.toHex(), and Uint8Array.prototype.setFromHex() for working with hex strings, where every byte is encoded by two characters, each one being either 0–9 or A–F (case-insensitive).
Constructor
Creates a new Uint8Array object.
Static properties
Also inherits static properties from its parent TypedArray.
Returns a number value of the element size. 1 in the case of Uint8Array.
Static methods
Inherits static methods from its parent TypedArray.
Creates a new Uint8Array object from a base64-encoded string.
Creates a new Uint8Array object from a hex-encoded string.
Instance properties
Also inherits instance properties from its parent TypedArray.
These properties are defined on Uint8Array.prototype and shared by all Uint8Array instances.
Uint8Array.prototype.BYTES_PER_ELEMENT
Returns a number value of the element size. 1 in the case of a Uint8Array.
Uint8Array.prototype.constructor
The constructor function that created the instance object. For Uint8Array instances, the initial value is the Uint8Array constructor.
Instance methods
Inherits instance methods from its parent TypedArray.
Uint8Array.prototype.setFromBase64()
Populates this Uint8Array object with bytes from a base64-encoded string, returning an object indicating how many bytes were read and written.
Uint8Array.prototype.setFromHex()
Populates this Uint8Array object with bytes from a hex-encoded string, returning an object indicating how many bytes were read and written.
Uint8Array.prototype.toBase64()
Returns a base64-encoded string based on the data in this Uint8Array object.
Returns a hex-encoded string based on the data in this Uint8Array object.
Examples
Different ways to create a Uint8Array
// From a length
const uint8 = new Uint8Array(2);
uint8[0] = 42;
console.log(uint8[0]); // 42
console.log(uint8.length); // 2
console.log(uint8.BYTES_PER_ELEMENT); // 1
// From an array
const x = new Uint8Array([21, 31]);
console.log(x[1]); // 31
// From another TypedArray
const y = new Uint8Array(x);
console.log(y[0]); // 21
// From an ArrayBuffer
const buffer = new ArrayBuffer(8);
const z = new Uint8Array(buffer, 1, 4);
console.log(z.byteOffset); // 1
// From an iterable
const iterable = (function* () {
yield* [1, 2, 3];
})();
const uint8FromIterable = new Uint8Array(iterable);
console.log(uint8FromIterable);
// Uint8Array [1, 2, 3]
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # table-49 |