TypedArray.prototype.buffer

// ArrayBuffer 
const buffer = new ArrayBuffer(8);
const uint16 = new Uint16Array(buffer);

console.log(uint16.buffer.byteLength);
// : 8

const buffer = new ArrayBuffer(8);
const uint16 = new Uint16Array(buffer);
uint16.buffer; // ArrayBuffer { byteLength: 8 }

const buffer = new ArrayBuffer(1024);
const arr = new Uint8Array(buffer, 64, 128);
console.log(arr.byteLength); // 128
console.log(arr.buffer.byteLength); // 1024
console.log(arr.buffer === buffer); // true