TypedArray

A TypedArray object describes an array-like view of an underlying binary data buffer. There is no global property named TypedArray, nor is there a directly visible TypedArray constructor.  Instead, there are a number of different global properties, whose values are typed array constructors for specific element types, listed below. On the following pages you will find common properties and methods that can be used with any typed array containing elements of any type.

Syntax

new TypedArray(length);
new TypedArray(typedArray);
new TypedArray(object);
new TypedArray(buffer [, byteOffset [, length]]);

where TypedArray() is one of:

Int8Array();
Uint8Array();
Uint8ClampedArray();
Int16Array();
Uint16Array();
Int32Array();
Uint32Array();
Float32Array();
Float64Array();

Parameters

length
When called with a length argument, a typed array containing length zeroes is created.
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.
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.

Description

ECMAScript 6 defines a TypedArray constructor that serves as the [[Prototype]] of all TypedArray constructors.  This constructor is not directly exposed: there is no global %TypedArray% or TypedArray property.  It is only directly accessible through Object.getPrototypeOf(Int8Array.prototype) and similar.  All TypedArrays constructors inherit common properties from the %TypedArray% constructor function.  Additionally, all typed array prototypes (TypedArray.prototype) have %TypedArray%.prototype as their [[Prototype]].

The %TypedArray% constructor on its own is not particularly useful.  Calling it or using it in a new expression will throw a TypeError, except when used during object creation in JS engines that support subclassing.  There are at present no such engines, so %TypedArray% is only useful to polyfill functions or properties onto all TypedArray constructors.

Property access

You can reference elements in the array using standard array index syntax (that is, using bracket notation). However, getting or setting indexed properties on typed arrays will not search in the prototype chain for this property, even when the indices are out of bound. Indexed properties will consult the ArrayBuffer and will never look at object properties. You can still use named properties, just like with all objects.

// Setting and getting using standard array syntax
var int16 = new Int16Array(2);
int16[0] = 42;
console.log(int16[0]); // 42

// Indexed properties on prototypes are not consulted (Fx 25)
Int8Array.prototype[20] = "foo";
(new Int8Array(32))[20]; // 0
// even when out of bound
Int8Array.prototype[20] = "foo";
(new Int8Array(8))[20]; // undefined
// or with negative integers
Int8Array.prototype[-1] = "foo";
(new Int8Array(8))[-1]; // undefined

// Named properties are allowed, though (Fx 30)
Int8Array.prototype.foo = "bar";
(new Int8Array(32)).foo; // "bar"

TypedArray objects

Type Size in bytes Description Web IDL type Equivalent C type
Int8Array 1 8-bit two's complement signed integer byte int8_t
Uint8Array 1 8-bit unsigned integer octet uint8_t
Uint8ClampedArray 1 8-bit unsigned integer (clamped) octet uint8_t
Int16Array 2 16-bit two's complement signed integer short int16_t
Uint16Array 2 16-bit unsigned integer unsigned short uint16_t
Int32Array 4 32-bit two's complement signed integer long int32_t
Uint32Array 4 32-bit unsigned integer unsigned long uint32_t
Float32Array 4 32-bit IEEE floating point number unrestricted float float
Float64Array 8 64-bit IEEE floating point number unrestricted double double

Properties

TypedArray.BYTES_PER_ELEMENT
Returns a number value of the element size for the different typed array objects.
TypedArray.length
Length property whose value is 3.
TypedArray.name
Returns the string value of the constructor name. E.g "Int8Array".
get TypedArray[@@species]
The constructor function that is used to create derived objects.
TypedArray.prototype
Prototype for the TypedArray objects.

Methods

TypedArray.from()
Creates a new typed array from an array-like or iterable object. See also Array.from().
TypedArray.of()
Creates a new typed array with a variable number of arguments. See also Array.of().

TypedArray prototype

All TypedArrays inherit from TypedArray.prototype.

Properties

{{page('en-US/Web/JavaScript/Reference/Global_Objects/TypedArray/prototype','Properties')}}

Methods

{{page('en-US/Web/JavaScript/Reference/Global_Objects/TypedArray/prototype','Methods')}}

Specifications

Specification Status Comment
Typed Array Specification Obsolete Defined as TypedArray and ArrayBufferView interface with typed array view types. Superseded by ECMAScript 6.
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'TypedArray Objects' in that specification.
Standard Initial definition in an ECMA standard. Specified behaviour for indexed and named properties. Specified that new is required.
ECMAScript (ECMA-262)
The definition of 'TypedArray Objects' in that specification.
Living Standard  

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 7.0 4.0 (2) 10 11.6 5.1
Indexed properties not consulting prototype (Yes) [1] 25 (25) ? ? ?
Named properties (Yes) 30 (30) ? ? ?
new is required ? 44 (44) ? ? ?
Feature Android Android Webview Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support 4.0 (Yes) 4.0 (2) 10 11.6 4.2 (Yes)
Indexed properties not consulting prototype ? (Yes) [1] 25.0 (25) ? ? ? (Yes) [1]
Named properties ? (Yes) 30.0 (30) ? ? ? ?
new is required ? ? 44.0 (44) ? ? ? ?

[1] -1 and similar are not considered as indexed properties and therefore return the value of the prototype property.

Compatibility notes

Starting with ECMAScript 2015 (ES6), TypedArray constructors require to be constructed with a new operator. Calling a TypedArray constructor as a function without new, will throw a TypeError from now on.

var dv = Int8Array([1, 2, 3]);
// TypeError: calling a builtin Int8Array constructor
// without new is forbidden
var dv = new Int8Array([1, 2, 3]);

See also