docs: function getQueryParameterValue(url, parameterName) {
          var parts;
          var query = (url || '').split('?');
          if (query && query.length > 0) {
              parts = query[1];
          }
          else {
              parts = '';
          }
          var vars = parts.split('&');
          for (var i = 0; i < vars.length; i++) {
              var pair = vars[i].split('=');
              if (decodeURIComponent(pair[0]) == parameterName) {
                  return decodeURIComponent(pair[1]);
              }
          }
          // not found
          return null;
      }