valor-software/ng2-bootstrap

<div class="btn-group" dropdown #dropdown="bs-dropdown" [autoClose]="false">
  <button dropdownToggle type="button" class="btn btn-primary dropdown-toggle">
    Button dropdown <span class="caret"></span>
  </button>
  <ul id="dropdown-triggers-manual" *dropdownMenu class="dropdown-menu"
      role="menu" aria-labelledby="button-triggers-manual">
    <li role="menuitem"><a class="dropdown-item" href="#">Action</a></li>
    <li role="menuitem"><a class="dropdown-item" href="#">Another action</a>
    </li>
    <li role="menuitem"><a class="dropdown-item" href="#">Something else
      here</a></li>
    <li class="divider dropdown-divider"></li>
  </ul>
</div>
<button type="button" class="btn btn-primary" (click)="dropdown.toggle(true)">Toggle</button>
<button type="button" class="btn btn-primary" (click)="dropdown.show()">Show</button>
<button type="button" class="btn btn-primary" (click)="dropdown.hide()">Hide</button>