getCookie.js

function getCookie(name) {
  let matches = document.cookie.match(new RegExp(
    "(?:^|; )" + name.replace(/([\.$?*|{}\(\)\[\]\\\/\+^])/g, '\\$1') + "=([^;]*)"
  ));
  if (!matches) {
    throw new Error('Cookie {0} not defined'.format(name));
  }
  return decodeURIComponent(matches[1]);
}