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 sizelength
multiplied byBYTES_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 asInt32Array
), thetypedArray
gets copied into a new typed array. Each value intypedArray
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 thetypedArray
argument. object
- When called with an
object
argument, a new typed array is created as if by theTypedArray.from()
method. buffer
,byteOffset
,length
- When called with a
buffer
, and optionally abyteOffset
and alength
argument, a new typed array view is created that views the specifiedArrayBuffer
. ThebyteOffset
andlength
parameters specify the memory range that will be exposed by the typed array view. If both are omitted, all ofbuffer
is viewed; if onlylength
is omitted, the remainder ofbuffer
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
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Uint8Array() constructor | Chrome Full support 7 | Edge Full support 12 | Firefox Full support 4 | IE Full support 10 | Opera Full support 11.6 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 12 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
Constructor without arguments | Chrome Full support 7 | Edge Full support 12 | Firefox Full support 55 | IE Full support 10 | Opera Full support 11.6 | Safari Full support 5.1 | WebView Android Full support ≤37 | Chrome Android Full support 18 | Firefox Android Full support 55 | Opera Android Full support 12 | Safari iOS Full support 5 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
new Uint8Array(iterable) | Chrome Full support 39 | Edge Full support 14 | Firefox Full support 52 | IE No support No | Opera Full support 26 | Safari Full support 10 | WebView Android Full support 39 | Chrome Android Full support 39 | Firefox Android Full support 52 | Opera Android Full support 26 | Safari iOS Full support 10 | Samsung Internet Android Full support 4.0 | nodejs Full support 4.0.0 |
Uint8Array() without new throws | Chrome Full support 7 | Edge Full support 14 | Firefox Full support 44 | IE No support No | Opera Full support 15 | Safari Full support 5.1 | WebView Android Full support ≤37 | Chrome Android Full support 18 | Firefox Android Full support 44 | Opera Android Full support 14 | Safari iOS Full support 5 | Samsung Internet Android Full support 1.0 | nodejs 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]);