discourse/app/assets/javascripts/select-kit/addon/components/period-chooser/period-chooser-header.js

import { classNames } from "@ember-decorators/component";
import discourseComputed from "discourse-common/utils/decorators";
import DropdownSelectBoxHeaderComponent from "select-kit/components/dropdown-select-box/dropdown-select-box-header";

@classNames("period-chooser-header", "btn-flat")
export default class PeriodChooserHeader extends DropdownSelectBoxHeaderComponent {
  @discourseComputed("selectKit.isExpanded")
  caretIcon(isExpanded) {
    return isExpanded ? "caret-up" : "caret-down";
  }
}