files/en-us/web/javascript/reference/global_objects/arraybuffer/bytelength/index.md

metadata

title: ArrayBuffer.prototype.byteLength
short-title: byteLength
slug: Web/JavaScript/Reference/Global_Objects/ArrayBuffer/byteLength
page-type: javascript-instance-accessor-property
browser-compat: javascript.builtins.ArrayBuffer.byteLength
sidebar: jsref

The byteLength accessor property of {{jsxref("ArrayBuffer")}} instances returns the length (in bytes) of this array buffer.

{{InteractiveExample("JavaScript Demo: ArrayBuffer.prototype.byteLength")}}

// Create an ArrayBuffer with a size in bytes
const buffer = new ArrayBuffer(8);

// Use byteLength to check the size
const bytes = buffer.byteLength;

console.log(bytes);
// Expected output: 8

Description

The byteLength property is an accessor property whose set accessor function is undefined, meaning that you can only read this property. The value is established when the array is constructed and cannot be changed. This property returns 0 if this ArrayBuffer has been detached.

Examples

Using byteLength

const buffer = new ArrayBuffer(8);
buffer.byteLength; // 8

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{jsxref("ArrayBuffer")}}