someDeclarativeMethod.js

function someDeclarativeMethod(setting, items, response) {
  var emptyMessage = {
    message: "You have not selected anything"
  };
  if (
    aService.isThisFooSetting(setting.type) &&
    !aService.isEditModeClear(setting.editMode) &&
    items.length === 0
  ) {
    response.errors.push(emptyMessage);
  }

  if (
    aService.isThisBarSetting(setting.type) &&
    !aService.isEditModeClear(setting.editMode) &&
    items.length === 0
  ) {
    response.errors.push(emptyMessage);
  }


  response.errors = items.reduce(errors, item => {
    const errs = item.checkForErrors();
    errs.length > 0 && errors.push(errs);
    return errors;
  }, []);

  return response;
}