const uint8 = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]);

// Insert position, start position, end position
uint8.copyWithin(3, 1, 3);

console.log(uint8);
// Expected output: Uint8Array [1, 2, 3, 2, 3, 6, 7, 8]