function getQueryParameter(name, url = window.location.href) {
  name = name.replace(/[\[\]]/g, '\\$&');
  const regex = new RegExp('[?&]' + name + '(=([^&#]*)|&|#|$)');
  const results = regex.exec(url);
  if (!results) return null;
  if (!results[2]) return '';
  return decodeURIComponent(results[2].replace(/\+/g, ' '));
}

// Example usage:
// const userId = getQueryParameter('user_id', 'https://example.com?name=John%20Doe&user_id=123');
// console.log(userId); // "123"