title: How to add arrow after/before content to Bootstrap button group with active class
body: <p>I am working on the below demo code. Why am I not able to add arrow content to the <code>active</code> btn in Bootstrap button group?</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>@import url("https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css");
  
  
  .btn-group .btn.active, .btn:active::after {
    content: "";
    position: absolute;
    border-bottom: 10px solid red;
    border-left: 10px solid #333;
    border-right: 10px solid #333;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="btn-group"&gt;
    &lt;button type="button" class="btn btn-default"&gt;One&lt;/button&gt;
    &lt;button type="button" class="btn btn-default"&gt;Two&lt;/button&gt;
    &lt;button type="button" class="btn btn-default"&gt;Three&lt;/button&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>