docs: function updateFieldsRec(toData, fromData) {
          var keys = Object.keys(fromData),
              i;
  
          for (i = 0; i < keys.length; i += 1) {
              if (isTrueObject(fromData[keys[i]]) && isTrueObject(toData[keys[i]])) {
                  updateFieldsRec(toData[keys[i]], fromData[keys[i]]);
              } else {
                  toData[keys[i]] = fromData[keys[i]];
              }
          }
      }