<nav id="sidebar" class="collapse navbar-collapse fixed-sidebar d-none d-md-block" [collapse]="!isNavCollapsed">
      <ul>
          <li>
              Some link
          </li>
     </ul>
   </nav>

<button class="navbar-dark navbar-toggler d-md-none" type="button" data-target="#sidebar" (click)="isNavCollapsed = !isNavCollapsed" aria-controls="navbarToggler" aria-expanded="false"
            aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
    </button>