nav.html

<!-- Define the site's nav bar w/Bootstrap's navbar component (https://getbootstrap.com/docs/4.1/components/navbar/). -->
<nav class="navbar navbar-expand-sm navbar-dark bg-dark">
  <div class="container">
    <a class="navbar-brand" href="{{ site.baseurl }}/"> 
      {{ site.title }} 
    </a>
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
      <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse justify-content-end" id="navbarNav">
      <ul class="navbar-nav">
      {% for item in site.data.nav %}  <!-- Loop through each item in the nav data, add to navbar. -->
        <li class="nav-item">
          <a class="nav-link {% if page.title == item.title %} active {% endif %}" href="{{ item.href | relative_url }}">{{ item.title }}</a>
        </li>
      {% endfor %}
      </ul>
    </div>
  </div>
</nav>