A typeahead example that gets values from the <code>WikipediaService</code>
<ul>
  <li>remote data retrieval</li>
  <li><code>debounceTime</code> operator</li>
  <li><code>do</code> operator</li>
  <li><code>distinctUntilChanged</code> operator</li>
  <li><code>switchMap</code> operator</li>
  <li><code>catch</code> operator to display an error message in case of connectivity issue</li>
</ul>

<div class="form-group">
  <label for="typeahead-http">Search for a wiki page:</label>
  <input id="typeahead-http" type="text" class="form-control" [class.is-invalid]="searchFailed" [(ngModel)]="model" [ngbTypeahead]="search" placeholder="Wikipedia search" />
  <span *ngIf="searching">searching...</span>
  <div class="invalid-feedback" *ngIf="searchFailed">Sorry, suggestions could not be loaded.</div>
</div>

<hr>
<pre>Model: {{ model | json }}</pre>