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 sizelength
multiplied byBYTES_PER_ELEMENT
bytes, containing zeros. typedArray
-
When called with a
typedArray
argument, which can be an object of any of the non-bigint 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 Language Specification # sec-typedarray-constructors |
Browser compatibility
BCD tables only load in the browser
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]);