Mod-97 Check Digit Calculation and Validation

export function mod97(input) {
  const digits = String(input).replace(/[\s-]/g, "");
  if (!/^\d+$/.test(digits)) throw new TypeError("input must contain digits only");
  let remainder = 0;
  for (const char of digits) {
    remainder = (remainder * 10 + Number(char)) % 97;
  }
  return remainder;
}

export function computeCheckDigits(base) {
  const digits = String(base).replace(/[\s-]/g, "");
  if (!/^\d+$/.test(digits)) throw new TypeError("base must contain digits only");
  const check = 98 - mod97(digits + "00");
  return String(check).padStart(2, "0");
}

export function validateCheckDigits(value) {
  const digits = String(value).replace(/[\s-]/g, "");
  if (!/^\d+$/.test(digits)) throw new TypeError("value must contain digits only");
  return mod97(digits) === 1;
}