code: protected function validateJsRemoteRequest($attribute, $parameters)
      {
          $this->setRemoteValidation($attribute, $parameters['validate_all']);
  
          $validator = $this->validator;
          if ($validator->passes()) {
              return true;
          }
  
          return $validator->messages()->get($attribute);
      }
docs: Validate remote Javascript Validations.
  
  @param $attribute
  @param array $parameters
  @return array|bool