---
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()")}}

```js interactive-example
// 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

```js-nolint
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](/en-US/docs/Glossary/Endianness) format. If `false` or `undefined`, a big-endian value is read.

### Return value

A {{jsxref("BigInt")}} from -2<sup>63</sup> to 2<sup>63</sup>-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()

```js
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](/en-US/docs/Web/JavaScript/Guide/Typed_arrays) guide
- {{jsxref("DataView")}}
- {{jsxref("ArrayBuffer")}}
- {{jsxref("BigInt64Array")}}