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.
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()
function to obtain a value with precision up to Number.MAX_SAFE_INTEGER
, which could suffice for certain cases.
function getUint64(dataview, byteOffset, littleEndian) { // split 64-bit number into two 32-bit (4-byte) parts const left = dataview.getUint32(byteOffset, littleEndian); const right = dataview.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; }
Alternatively, if you need full 64-bit range, you can create a BigInt
. Further, although native BigInts are much faster than user-land library equivalents, BigInts will always be much slower than 32-bit integers in JavaScript due to the nature of their variable size.
const BigInt = window.BigInt, bigThirtyTwo = BigInt(32), bigZero = BigInt(0); function getUint64BigInt(dataview, byteOffset, littleEndian) { // split 64-bit number into two 32-bit (4-byte) parts const left = BigInt(dataview.getUint32(byteOffset|0, !!littleEndian)>>>0); const right = BigInt(dataview.getUint32((byteOffset|0) + 4|0, !!littleEndian)>>>0); // combine the two 32-bit values and return return littleEndian ? (right<<bigThirtyTwo)|left : (left<<bigThirtyTwo)|right; }
Constructor
DataView()
- Creates a new
DataView
object.
Instance properties
DataView.prototype.buffer
- The
ArrayBuffer
referenced by this view. Fixed at construction time and thus read only. DataView.prototype.byteLength
- The length (in bytes) of this view from the start of its
ArrayBuffer
. Fixed at construction time and thus read only. DataView.prototype.byteOffset
- The offset (in bytes) of this view from the start of its
ArrayBuffer
. Fixed at construction time and thus read only.
Instance methods
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.
DataView.prototype.getBigInt64()
- Gets a signed 64-bit integer (long long) at the specified byte offset from the start of the view.
DataView.prototype.getBigUint64()
- Gets an unsigned 64-bit integer (unsigned long long) at the specified byte offset from the start of the view.
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.
DataView.prototype.setBigInt64()
- Stores a signed 64-bit integer (long long) value at the specified byte offset from the start of the view.
DataView.prototype.setBigUint64()
- Stores an unsigned 64-bit integer (unsigned long long) value at the specified byte offset from the start of the view.
Examples
Using DataView
var buffer = new ArrayBuffer(16); var view = new DataView(buffer, 0); view.setInt16(1, 42); view.getInt16(1); // 42
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'DataView' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
DataView | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
DataView() constructor | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
buffer | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
byteLength | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
byteOffset | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
getBigInt64 | Chrome Full support 67 | Edge Full support 79 | Firefox Full support 68 | IE No support No | Opera Full support 54 | Safari No support No | WebView Android Full support 67 | Chrome Android Full support 67 | Firefox Android Full support 68 | Opera Android Full support 48 | Safari iOS No support No | Samsung Internet Android Full support 9.0 | nodejs Full support 10.4.0 |
getBigUint64 | Chrome Full support 67 | Edge Full support 79 | Firefox Full support 68 | IE No support No | Opera Full support 54 | Safari No support No | WebView Android Full support 67 | Chrome Android Full support 67 | Firefox Android Full support 68 | Opera Android Full support 48 | Safari iOS No support No | Samsung Internet Android Full support 9.0 | nodejs Full support 10.4.0 |
getFloat32 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
getFloat64 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
getInt16 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
getInt32 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
getInt8 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
getUint16 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
getUint32 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
getUint8 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
setBigInt64 | Chrome Full support 67 | Edge Full support 79 | Firefox Full support 68 | IE No support No | Opera Full support 54 | Safari No support No | WebView Android Full support 67 | Chrome Android Full support 67 | Firefox Android Full support 68 | Opera Android Full support 48 | Safari iOS No support No | Samsung Internet Android Full support 9.0 | nodejs Full support 10.4.0 |
setBigUint64 | Chrome Full support 67 | Edge Full support 79 | Firefox Full support 68 | IE No support No | Opera Full support 54 | Safari No support No | WebView Android Full support 67 | Chrome Android Full support 67 | Firefox Android Full support 68 | Opera Android Full support 48 | Safari iOS No support No | Samsung Internet Android Full support 9.0 | nodejs Full support 10.4.0 |
setFloat32 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
setFloat64 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
setInt16 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
setInt32 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
setInt8 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
setUint16 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
setUint32 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
setUint8 | Chrome Full support 9 | Edge Full support 12 | Firefox Full support 15 | IE Full support 10 | Opera Full support 12.1 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 15 | Opera Android Full support 12.1 | Safari iOS Full support 4.2 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.10 |
Legend
- Full support
- Full support
- No support
- No support
See also
- jDataView: JavaScript library that polyfills and extends the
DataView
API to all browsers and Node.js. ArrayBuffer
SharedArrayBuffer