files/en-us/web/javascript/reference/global_objects/dataview/getbigint64/index.md

metadata

title: DataView.prototype.getBigInt64()
short-title: getBigInt64()
slug: Web/JavaScript/Reference/Global_Objects/DataView/getBigInt64
page-type: javascript-instance-method
browser-compat: javascript.builtins.DataView.getBigInt64
sidebar: jsref

The getBigInt64() method of {{jsxref("DataView")}} instances reads 8 bytes starting at the specified byte offset of this DataView and interprets them as a 64-bit signed integer. There is no alignment constraint; multi-byte values may be fetched from any offset within bounds.

{{InteractiveExample("JavaScript Demo: DataView.prototype.getBigInt64()")}}

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

// Highest possible BigInt value that fits in a signed 64-bit integer
const max = 2n ** (64n - 1n) - 1n;

const view = new DataView(buffer);
view.setBigInt64(1, max);

console.log(view.getBigInt64(1));
// Expected output: 9223372036854775807n

Syntax

getBigInt64(byteOffset)
getBigInt64(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 -2⁶³ to 2⁶³-1, inclusive.

Exceptions

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

Examples

Using getBigInt64()

const { buffer } = new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
const dataview = new DataView(buffer);
console.log(dataview.getBigInt64(1)); // 72623859790382856n

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• JavaScript typed arrays guide
• {{jsxref("DataView")}}
• {{jsxref("ArrayBuffer")}}
• {{jsxref("BigInt64Array")}}