<li *ngFor="let item of IndexChap; let i = index">

              <!-- path route -->
              <a routerLink="/tableofcontents/{{item.name}}"> <span class='chapters'> {{i+1}}</span>
            . <span> {{item.name}}</span>
            </a>


            <ul *ngFor="let subItem of item.subItems"[attr.id]='subItem'>
              <li>
                <a [routerLink]="['/tableofcontents', subItem.name]" [fragment]="subItem.name"> {{ subItem.name }}</a>
              </li>
            </ul>