Våra volontärer har inte översatt denna artikel till Svenska ännu. Gå med oss och hjälpa till att få jobbet gjort!
Du kan också läsa artikeln på English (US).

The DataView view provides a low-level interface for reading and writing multiple number types in a binary ArrayBuffer, without having to care about the platform's endianness.

Syntax

new DataView(buffer [, byteOffset [, byteLength]])

Parameters

buffer
An existing ArrayBuffer or SharedArrayBuffer to use as the storage backing the new DataView object.
byteOffset Optional
The offset, in bytes, to the first byte in the above buffer for the new view to reference. If unspecified, the buffer view starts with the first byte.
byteLength Optional
The number of elements in the byte array. If unspecified, the view's length will match the buffer's length.

Return value

A new DataView object representing the specified data buffer. (That probably wasn't a very helpful description.)

You can think of the returned object as an "interpreter" of the array buffer of bytes — it knows how to convert numbers to fit within the buffer correctly, both when reading and writing to it. This means handling integer and float conversion, endianness, and other details of representing numbers in binary form.

Exceptions

RangeError

Thrown if the byteOffset or byteLength parameter values result in the view extending past the end of the buffer.

For example, if the buffer is 16 bytes long, the byteOffset is 8, and the byteLength is 10, this error is thrown because the resulting view tries to extend 2 bytes past the total length of the buffer.

Description

Endianness

Multi-byte number formats are represented in memory differently depending on machine architecture — see Endianness for an explanation. DataView accessors provide explicit control of how data is accessed, regardless of the executing computer's endianness.

var littleEndian = (function() {
  var buffer = new ArrayBuffer(2);
  new DataView(buffer).setInt16(0, 256, true /* littleEndian */);
  // Int16Array uses the platform's endianness.
  return new Int16Array(buffer)[0] === 256;
})();
console.log(littleEndian); // true or false

64-bit Integer Values

Because JavaScript does not currently include standard support for 64-bit integer values, DataView does not offer native 64-bit operations.  As a workaround, you could implement your own getUint64() method to obtain a value with precision up to Number.MAX_SAFE_INTEGER, which could suffice for certain cases.

DataView.prototype.getUint64 = function(byteOffset, littleEndian) {
  // split 64-bit number into two 32-bit (4-byte) parts
  const left =  this.getUint32(byteOffset, littleEndian);
  const right = this.getUint32(byteOffset+4, littleEndian);

  // combine the two 32-bit values
  const combined = littleEndian? left + 2**32*right : 2**32*left + right;

  if (!Number.isSafeInteger(combined))
    console.warn(combined, 'exceeds MAX_SAFE_INTEGER. Precision may be lost');

  return combined;
}

 

Properties

All DataView instances inherit from DataView.prototype and allows the addition of properties to all DataView objects.

DataView.prototype.constructor
Specifies the function that creates an object's prototype. The initial value is the standard built-in DataView constructor.
DataView.prototype.buffer Read only
The ArrayBuffer referenced by this view. Fixed at construction time and thus read only.
DataView.prototype.byteLength Read only
The length (in bytes) of this view from the start of its ArrayBuffer. Fixed at construction time and thus read only.
DataView.prototype.byteOffset Read only
The offset (in bytes) of this view from the start of its ArrayBuffer. Fixed at construction time and thus read only.

Methods

Read

DataView.prototype.getInt8()
Gets a signed 8-bit integer (byte) at the specified byte offset from the start of the view.
DataView.prototype.getUint8()
Gets an unsigned 8-bit integer (unsigned byte) at the specified byte offset from the start of the view.
DataView.prototype.getInt16()
Gets a signed 16-bit integer (short) at the specified byte offset from the start of the view.
DataView.prototype.getUint16()
Gets an unsigned 16-bit integer (unsigned short) at the specified byte offset from the start of the view.
DataView.prototype.getInt32()
Gets a signed 32-bit integer (long) at the specified byte offset from the start of the view.
DataView.prototype.getUint32()
Gets an unsigned 32-bit integer (unsigned long) at the specified byte offset from the start of the view.
DataView.prototype.getFloat32()
Gets a signed 32-bit float (float) at the specified byte offset from the start of the view.
DataView.prototype.getFloat64()
Gets a signed 64-bit float (double) at the specified byte offset from the start of the view.

Write

DataView.prototype.setInt8()
Stores a signed 8-bit integer (byte) value at the specified byte offset from the start of the view.
DataView.prototype.setUint8()
Stores an unsigned 8-bit integer (unsigned byte) value at the specified byte offset from the start of the view.
DataView.prototype.setInt16()
Stores a signed 16-bit integer (short) value at the specified byte offset from the start of the view.
DataView.prototype.setUint16()
Stores an unsigned 16-bit integer (unsigned short) value at the specified byte offset from the start of the view.
DataView.prototype.setInt32()
Stores a signed 32-bit integer (long) value at the specified byte offset from the start of the view.
DataView.prototype.setUint32()
Stores an unsigned 32-bit integer (unsigned long) value at the specified byte offset from the start of the view.
DataView.prototype.setFloat32()
Stores a signed 32-bit float (float) value at the specified byte offset from the start of the view.
DataView.prototype.setFloat64()
Stores a signed 64-bit float (double) value at the specified byte offset from the start of the view.

Example

var buffer = new ArrayBuffer(16);
var view = new DataView(buffer, 0);

view.setInt16(1, 42);
view.getInt16(1); // 42

Specifications

Specification Status Comment
Typed Array Specification Obsolete Superseded by ECMAScript 6
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'DataView' in that specification.
Standard Initial definition in an ECMA standard
ECMAScript Latest Draft (ECMA-262)
The definition of 'DataView' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
DataView() without new throwsChrome Full support YesEdge Full support YesFirefox Full support 40IE No support NoOpera Full support YesSafari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 40Opera Android ? Safari iOS ? Samsung Internet Android ? nodejs Full support 0.12
SharedArrayBuffer accepted as bufferChrome Full support 60Edge ? Firefox Full support 55IE ? Opera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 55Opera Android ? Safari iOS ? Samsung Internet Android ? nodejs ?
bufferChrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
byteLengthChrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
byteOffsetChrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
getFloat32Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
getFloat64Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
getInt16Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
getInt32Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
getInt8Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
getUint16Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
getUint32Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
getUint8Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
setFloat32Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
setFloat64Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
setInt16Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
setInt32Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
setInt8Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
setUint16Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
setUint32Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
setUint8Chrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes
prototypeChrome Full support 9Edge Full support 12Firefox Full support 15IE Full support 10Opera Full support 12.1Safari Full support 5.1WebView Android Full support 4Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 15Opera Android Full support 12Safari iOS Full support 4.2Samsung Internet Android Full support Yesnodejs Full support Yes

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown

Compatibility notes

Starting with Firefox 40, DataView must be constructed with the new operator. Calling DataView() as a function without new will throw a TypeError.

var view = DataView(buffer, 0); 
// TypeError: calling a builtin DataView constructor without new is forbidden
var view = new DataView(buffer, 0);

See also

Dokumenttaggar och bidragare

Senast uppdaterad av: anthumchris,