DataView.prototype.setBigInt64()

// Create an ArrayBuffer with a size in bytes
const buffer = new ArrayBuffer(16);

// Highest possible BigInt value that fits in a signed 64-bit integer
const max = 2n ** (64n - 1n) - 1n;

const view = new DataView(buffer);
view.setBigInt64(1, max);

console.log(view.getBigInt64(1));
// Expected output: 9223372036854775807n

setBigInt64(byteOffset, value)
setBigInt64(byteOffset, value, littleEndian)

const buffer = new ArrayBuffer(10);
const dataview = new DataView(buffer);
dataview.setBigInt64(0, 3n);
dataview.getBigInt64(1); // 768n