TypedArray.prototype.byteLength
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The byteLength accessor property of TypedArray instances returns the length (in bytes) of this typed array.
Try it
// Create an ArrayBuffer with a size in bytes
const buffer = new ArrayBuffer(8);
const uint8 = new Uint8Array(buffer, 2);
console.log(uint8.byteLength);
// Expected output: 6
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 a TypedArray is constructed and cannot be changed. If the TypedArray is not specifying a byteOffset or a length, the length of the referenced ArrayBuffer will be returned. TypedArray is one of the TypedArray objects.
Examples
Using the byteLength property
js
const buffer = new ArrayBuffer(8);
const uint8 = new Uint8Array(buffer);
uint8.byteLength; // 8 (matches the byteLength of the buffer)
const uint8newLength = new Uint8Array(buffer, 1, 5);
uint8newLength.byteLength; // 5 (as specified when constructing the Uint8Array)
const uint8offSet = new Uint8Array(buffer, 2);
uint8offSet.byteLength; // 6 (due to the offset of the constructed Uint8Array)
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-get-%typedarray%.prototype.bytelength |