title: Open tag not working in Angular 6.4.1 version
body: <p>I have just started learning Angual JS and following one of the tutorial for hands on.</p>
  
  <p>In the example they have mentioned the below code which is not working for me. In the below example  class="btn-group open" is unable to open the drop-down. I tried using show instead of open but it didn't work.</p>
  
  <p>What I suppose to do make it work?</p>
  
  <pre><code>&lt;div class="row"&gt;
    &lt;div class="col-12"&gt;
      &lt;div class="btn-group open"&gt;
        &lt;button type="button" 
        class="btn btn-primary dropdown-toggle"&gt;
        Manage Recipe &lt;span class="caret"&gt;&lt;/span&gt;
      &lt;/button&gt;
      &lt;ul class="dropdown-menu"&gt;
        &lt;li&gt;&lt;a href="#"&gt;To Shopping List&lt;/a&gt;&lt;/li&gt;
        &lt;li&gt;&lt;a href="#"&gt;Edit Recipe&lt;/a&gt;&lt;/li&gt;
        &lt;li&gt;&lt;a href="#"&gt;Delete Recipe&lt;/a&gt;&lt;/li&gt;
      &lt;/ul&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>