files/en-us/web/javascript/reference/global_objects/dataview/getbiguint64/index.md

metadata

title: DataView.prototype.getBigUint64()
short-title: getBigUint64()
slug: Web/JavaScript/Reference/Global_Objects/DataView/getBigUint64
page-type: javascript-instance-method
browser-compat: javascript.builtins.DataView.getBigUint64
sidebar: jsref

The getBigUint64() method of {{jsxref("DataView")}} instances reads 8 bytes starting at the specified byte offset of this DataView and interprets them as a 64-bit unsigned integer. There is no alignment constraint; multi-byte values may be fetched from any offset within bounds.

{{InteractiveExample("JavaScript Demo: DataView.prototype.getBigUint64()")}}

// Create an ArrayBuffer with a size in bytes
const buffer = new ArrayBuffer(16);

// Highest possible BigInt value that fits in an unsigned 64-bit integer
const max = 2n ** 64n - 1n;

const view = new DataView(buffer);
view.setBigUint64(1, max);

console.log(view.getBigUint64(1));
// Expected output: 18446744073709551615n

Syntax

getBigUint64(byteOffset)
getBigUint64(byteOffset, littleEndian)

Parameters

• byteOffset
  • : The offset, in bytes, from the start of the view to read the data from.
• littleEndian {{optional_inline}}
  • : Indicates whether the data is stored in little- or big-endian format. If false or undefined, a big-endian value is read.

Return value

A {{jsxref("BigInt")}} from 0 to 2⁶⁴-1, inclusive.

Exceptions

• {{jsxref("RangeError")}}
  • : Thrown if the byteOffset is set such that it would read beyond the end of the view.

Examples

Using getBigUint64()

const { buffer } = new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
const dataview = new DataView(buffer);
console.log(dataview.getBigUint64(1)); // 72623859790382856n

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• JavaScript typed arrays guide
• {{jsxref("DataView")}}
• {{jsxref("ArrayBuffer")}}
• {{jsxref("BigUint64Array")}}