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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 internal array buffer is created in memory of size length multiplied by BYTES_PER_ELEMENT bytes containing 0 value. - 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. Then length of the new typedArray object will be same of length of the typedArray 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.
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)
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.
When creating a TypedArray instance (i.e. instance of Int8Array or similar), a array buffer is created internally (if ArrayBuffer object is present as constructor argument then this array buffer is used) in memory and this buffer address is saved as internal property of that instances, and all the methods of %TypedArray
%.prototype
uses that array buffer address to operate on i.e. set value and get value etc.
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
TypedArray.prototype.constructor
- Returns the function that created an instance's prototype. This is one the corresponding typed array type functions by default.
TypedArray.prototype.buffer
Read only- Returns the
ArrayBuffer
referenced by the typed array. Fixed at construction time and thus read only. TypedArray.prototype.byteLength
Read only- Returns the length (in bytes) of the typed array from the start of its
ArrayBuffer
. Fixed at construction time and thus read only. TypedArray.prototype.byteOffset
Read only- Returns the offset (in bytes) of the typed array from the start of its
ArrayBuffer
. Fixed at construction time and thus read only. TypedArray.prototype.length
Read only- Returns the number of elements hold in the typed array. Fixed at construction time and thus read only.
Methods
TypedArray.prototype.copyWithin()
- Copies a sequence of array elements within the array. See also
Array.prototype.copyWithin()
. TypedArray.prototype.entries()
- Returns a new
Array Iterator
object that contains the key/value pairs for each index in the array. See alsoArray.prototype.entries()
. TypedArray.prototype.every()
- Tests whether all elements in the array pass the test provided by a function. See also
Array.prototype.every()
. TypedArray.prototype.fill()
- Fills all the elements of an array from a start index to an end index with a static value. See also
Array.prototype.fill()
. TypedArray.prototype.filter()
- Creates a new array with all of the elements of this array for which the provided filtering function returns true. See also
Array.prototype.filter()
. TypedArray.prototype.find()
- Returns the found value in the array, if an element in the array satisfies the provided testing function or
undefined
if not found. See alsoArray.prototype.find()
. TypedArray.prototype.findIndex()
- Returns the found index in the array, if an element in the array satisfies the provided testing function or -1 if not found. See also
Array.prototype.findIndex()
. TypedArray.prototype.forEach()
- Calls a function for each element in the array. See also
Array.prototype.forEach()
. TypedArray.prototype.includes()
- Determines whether a typed array includes a certain element, returning
true
orfalse
as appropriate. See alsoArray.prototype.includes()
. TypedArray.prototype.indexOf()
- Returns the first (least) index of an element within the array equal to the specified value, or -1 if none is found. See also
Array.prototype.indexOf()
. TypedArray.prototype.join()
- Joins all elements of an array into a string. See also
Array.prototype.join()
. TypedArray.prototype.keys()
- Returns a new
Array Iterator
that contains the keys for each index in the array. See alsoArray.prototype.keys()
. TypedArray.prototype.lastIndexOf()
- Returns the last (greatest) index of an element within the array equal to the specified value, or -1 if none is found. See also
Array.prototype.lastIndexOf()
. TypedArray.prototype.map()
- Creates a new array with the results of calling a provided function on every element in this array. See also
Array.prototype.map()
. TypedArray.prototype.move()
Unimplemented- Former non-standard version of
TypedArray.prototype.copyWithin()
. TypedArray.prototype.reduce()
- Apply a function against an accumulator and each value of the array (from left-to-right) as to reduce it to a single value. See also
Array.prototype.reduce()
. TypedArray.prototype.reduceRight()
- Apply a function against an accumulator and each value of the array (from right-to-left) as to reduce it to a single value. See also
Array.prototype.reduceRight()
. TypedArray.prototype.reverse()
- Reverses the order of the elements of an array — the first becomes the last, and the last becomes the first. See also
Array.prototype.reverse()
. TypedArray.prototype.set()
- Stores multiple values in the typed array, reading input values from a specified array.
TypedArray.prototype.slice()
- Extracts a section of an array and returns a new array. See also
Array.prototype.slice()
. TypedArray.prototype.some()
- Returns true if at least one element in this array satisfies the provided testing function. See also
Array.prototype.some()
. TypedArray.prototype.sort()
- Sorts the elements of an array in place and returns the array. See also
Array.prototype.sort()
. TypedArray.prototype.subarray()
- Returns a new TypedArray from the given start and end element index.
TypedArray.prototype.values()
- Returns a new
Array Iterator
object that contains the values for each index in the array. See alsoArray.prototype.values()
. TypedArray.prototype.toLocaleString()
- Returns a localized string representing the array and its elements. See also
Array.prototype.toLocaleString()
. TypedArray.prototype.toString()
- Returns a string representing the array and its elements. See also
Array.prototype.toString()
. TypedArray.prototype[@@iterator]()
- Returns a new
Array Iterator
object that contains the values for each index in the array.
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 2017 Draft (ECMA-262) The definition of 'TypedArray Objects' in that specification. |
Draft |
Browser compatibility
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]);