function getParameterByName(name, url) {
  if (!url) url = window.location.href;
  name = name.replace(/[[]]/g, '\\$&');
  var regex = new RegExp('[?&]' + name + '(=([^&#]*)|&|#|$)'),
      results = regex.exec(url);
  if (!results) return null;
  if (!results[2]) return '';
  return decodeURIComponent(results[2].replace(/\+/g, ' '));
}
Get URL parameter by name.
@function
@param {string} name - Name of parameter.
@param {string} url - URL
@returns {string} Parameter value