---
title: DataView.prototype.setFloat64()
short-title: setFloat64()
slug: Web/JavaScript/Reference/Global_Objects/DataView/setFloat64
page-type: javascript-instance-method
browser-compat: javascript.builtins.DataView.setFloat64
sidebar: jsref
---

The **`setFloat64()`** method of {{jsxref("DataView")}} instances takes a number and stores it as a 64-bit floating point number in the 8 bytes starting at the specified byte offset of this `DataView`. There is no alignment constraint; multi-byte values may be stored at any offset within bounds.

{{InteractiveExample("JavaScript Demo: DataView.prototype.setFloat64()")}}

```js interactive-example
// Create an ArrayBuffer with a size in bytes
const buffer = new ArrayBuffer(16);

const view = new DataView(buffer);
view.setFloat64(1, Math.PI);

console.log(view.getFloat64(1));
// Expected output: 3.141592653589793
```

## Syntax

```js-nolint
setFloat64(byteOffset, value)
setFloat64(byteOffset, value, littleEndian)
```

### Parameters

- `byteOffset`
  - : The offset, in bytes, from the start of the view to store the data in.
- `value`
  - : The value to set. For how the value is encoded in bytes, see [Value encoding and normalization](/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray#value_encoding_and_normalization).
- `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 written.

### Return value

{{jsxref("undefined")}}.

### Exceptions

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

## Examples

### Using setFloat64()

```js
const buffer = new ArrayBuffer(10);
const dataview = new DataView(buffer);
dataview.setFloat64(0, 3);
dataview.getFloat64(1); // 3.785766995733679e-270
```

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [JavaScript typed arrays](/en-US/docs/Web/JavaScript/Guide/Typed_arrays) guide
- {{jsxref("DataView")}}
- {{jsxref("ArrayBuffer")}}
- {{jsxref("Float64Array")}}