{% assign currentUrl = page.url | replace: ".html" "" %}

{% for section in site.data.navigation.toc %}
<div>
  <strong>{{ section.section }}</strong>
  <ul>
    {% for subpage in section.subpages %}
        <li>
          <a href="{{ subpage.url | prepend:site.baseurl }}"{% if currentUrl == subpage.url %} class="active"{% endif %}>{{ subpage.page }}</a>
        </li>
    {% endfor %}
  </ul>
</div>
{% endfor %}