title: Collapse button is not showing for Bootstrap navbar
body: <pre><code>&lt;nav role="navigation" class="navbar navbar-default navbar-fixed-top"&gt;
      &lt;div class="container-fluid"&gt;
          &lt;div class="navbar-header"&gt;
              &lt;a href="" class="navbar-brand"&gt;Online Notes&lt;/a&gt;
              &lt;button type="button" class="navbar-toggle"&gt;
                  &lt;span class="sr-only"&gt;Toggle Navigation&lt;/span&gt;
                  &lt;span class="icon-bar"&gt;&lt;/span&gt;
                  &lt;span class="icon-bar"&gt;&lt;/span&gt;
                  &lt;span class="icon-bar"&gt;&lt;/span&gt;
              &lt;/button&gt;
          &lt;/div&gt;
          &lt;div class="navbar-collapse collapse"&gt;
  
          &lt;/div&gt;
      &lt;/div&gt;
  &lt;/nav&gt;
  </code></pre>
  
  <p>I am new to bootstrap and when I try to add a navbar using bootstrap, the collapse menu is not showing the three icon-bar. Can you help me? Thanks in advance.</p>