DataView

The DataView view provides a low-level interface for reading and writing multiple number types in an ArrayBuffer irrespective of the platform's endianness.

Syntax

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

Parameters

buffer

An existing ArrayBuffer or SharedArrayBuffer to use as the storage for the new DataView object.

byteOffset Optional

The offset, in bytes, to the first byte in the specified buffer for the new view to reference. If not specified, the view of the buffer will start with the first byte.

byteLength Optional

The number of elements in the byte array. If unspecified, length of the view will match the buffer's length.

Return value

A new DataView object representing the specified data buffer.

Exceptions

RangeError

Thrown if the byteOffset and byteLength result in the specified view extending past the end 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 will be accessed irrespective of the platform architecture'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

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 dv = new DataView(buffer, 0);
dv.setInt16(1, 42);
dv.getInt16(1); //42

Specifications

Browser compatibility

[1] The Shared memory feature is disabled by a preference setting. In about:config, set javascript.options.shared_memory to true. 

Compatibility notes

Starting with Gecko / SpiderMonkey 40 (Firefox 40 / Thunderbird 40 / SeaMonkey 2.37), DataView requires to be constructed with a new operator. Calling DataView() as a function without new, will throw a TypeError from now on.

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

var dv = new DataView(buffer, 0);

See also

• jDataView: JavaScript library that polyfills and extends the DataView API to all browsers and Node.js.
• ArrayBuffer
• SharedArrayBuffer