DataView.prototype.setBigInt64()

// ArrayBuffer 
const buffer = new ArrayBuffer(16);

//  64 
const max = 2n ** (64n - 1n) - 1n;

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

console.log(view.getBigInt64(1));
// : 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