Uint8Array() constructor

The Uint8Array() constructor creates a typed array of 8-bit unsigned integers. The contents are initialized to 0. 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).

Syntax

new Uint8Array(); // new in ES2017
new Uint8Array(length);
new Uint8Array(typedArray);
new Uint8Array(object);

new Uint8Array(buffer);
new Uint8Array(buffer, byteOffset);
new Uint8Array(buffer, byteOffset, length);

Parameters

length: When called with a length argument, an internal array buffer is created in memory, of size length multiplied by BYTES_PER_ELEMENT bytes, containing zeros.
typedArray: When called with a typedArray argument, which can be an object of any of the typed array types (such as Int32Array), the typedArray gets copied into a new typed array. Each value in typedArray is converted to the corresponding type of the constructor before being copied into the new array. The length of the new typed array will be same as the length of the typedArray argument.
object: When called with an object argument, a new typed array is created as if by the TypedArray.from() method.
buffer, byteOffset, length: When called with a buffer, and optionally a byteOffset and a length argument, a new typed array view is created that views the specified ArrayBuffer. The byteOffset and length parameters specify the memory range that will be exposed by the typed array view. If both are omitted, all of buffer is viewed; if only length is omitted, the remainder of buffer is viewed.

Examples

Different ways to create a Uint8Array

// From a length
var 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
var arr = new Uint8Array([21,31]);
console.log(arr[1]); // 31

// From another TypedArray
var x = new Uint8Array([21, 31]);
var y = new Uint8Array(x);
console.log(y[0]); // 21

// From an ArrayBuffer
var buffer = new ArrayBuffer(8);
var z = new Uint8Array(buffer, 1, 4);

// From an iterable
var iterable = function*(){ yield* [1,2,3]; }();
var uint8 = new Uint8Array(iterable);
// Uint8Array[1, 2, 3]

Specifications

Specification
ECMAScript Language Specification (ECMAScript) # sec-typedarray-constructors

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`Uint8Array`	7	12	4	10	11.6	5.1	4	18	4	12	4.2	1.0
`constructor_without_parameters`	7	12	55	10	11.6	5.1	≤37	18	55	12	5	1.0
`iterable_allowed`	39	14	52	No	26	10	39	39	52	26	10	4.0
`new_required`	7	14	44	No	15	5.1	≤37	18	44	14	5	1.0

Compatibility notes

Starting with ECMAScript 2015, Uint8Array constructors require to be constructed with a new operator. Calling a Uint8Array constructor as a function without new, will throw a TypeError from now on.

var dv = Uint8Array([1, 2, 3]);
// TypeError: calling a builtin Uint8Array constructor
// without new is forbidden

var dv = new Uint8Array([1, 2, 3]);