en_btr_frontend/app/components/chapter.js

import Component from '@glimmer/component';
import { tracked } from "@glimmer/tracking";
import { action } from '@ember/object';
import { inject as service } from '@ember/service';


export default class ChapterComponent extends Component {
  @service('nav-state') navState;

  @action
  selectChapter() {
    this.args.showVerses(this.args.book, this.args.chapter);
    this.navState.setChapter(this.args.chapter);
  }

  get
  selected() {
    if(this.navState.isCurrentChapter(this.args.chapter)) {
      return "selected";
    } else {
      return "";
    }
  }
}