function pageLimit(url) {
  const values = url.searchParams.getAll('limit');
  if (values.length === 0) return 10;
  if (values.length !== 1 || !/^[1-9][0-9]?$/.test(values[0]))
    throw new Error('Invalid limit');
  const limit = Number(values[0]);
  if (limit > 20) throw new Error('Invalid limit');
  return limit;
}
console.log(pageLimit(new URL('http://desk.invalid/kits?limit=2')));
try {
  pageLimit(new URL('http://desk.invalid/kits?limit=2&limit=3'));
} catch (error) {
  console.log(error.message);
}