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 [, 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 (ECMA-262)
The definition of 'TypedArray constructors' in that specification.

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
Uint8Array() constructorChrome Full support 7Edge Full support 12Firefox Full support 4IE Full support 10Opera Full support 11.6Safari Full support 5.1WebView Android Full support 4Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support 1.0nodejs Full support 0.10
Constructor without argumentsChrome Full support 7Edge Full support 12Firefox Full support 55IE Full support 10Opera Full support 11.6Safari Full support 5.1WebView Android Full support ≤37Chrome Android Full support 18Firefox Android Full support 55Opera Android Full support 12Safari iOS Full support 5Samsung Internet Android Full support 1.0nodejs Full support 0.10
new Uint8Array(iterable)Chrome Full support 39Edge Full support 14Firefox Full support 52IE No support NoOpera Full support 26Safari Full support 10WebView Android Full support 39Chrome Android Full support 39Firefox Android Full support 52Opera Android Full support 26Safari iOS Full support 10Samsung Internet Android Full support 4.0nodejs Full support 4.0.0
Uint8Array() without new throwsChrome Full support 7Edge Full support 14Firefox Full support 44IE No support NoOpera Full support 15Safari Full support 5.1WebView Android Full support ≤37Chrome Android Full support 18Firefox Android Full support 44Opera Android Full support 14Safari iOS Full support 5Samsung Internet Android Full support 1.0nodejs Full support 0.12

Legend

Full support  
Full support
No support  
No support

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]);

See also