Constant-Time String Comparison

const encoder = new TextEncoder();

// Constant-time comparison for secrets and signatures.
export function constantTimeEqual(left, right) {
  const a = encoder.encode(String(left));
  const b = encoder.encode(String(right));
  const length = Math.max(a.length, b.length);
  let difference = a.length ^ b.length;
  for (let index = 0; index < length; index += 1) {
    difference |= (a[index] ?? 0) ^ (b[index] ?? 0);
  }
  return difference === 0;
}

export function constantTimeEqualBytes(left, right) {
  if (!(left instanceof Uint8Array) || !(right instanceof Uint8Array)) {
    throw new TypeError("both arguments must be Uint8Array values");
  }
  const length = Math.max(left.length, right.length);
  let difference = left.length ^ right.length;
  for (let index = 0; index < length; index += 1) {
    difference |= (left[index] ?? 0) ^ (right[index] ?? 0);
  }
  return difference === 0;
}