Bootstrap 4 navbar for Shopify Theme

navbar.liquid

  <nav class="navbar navbar-expand-lg navbar-light bg-light">
      <a class="navbar-brand" href="#">Navbar</a>
      <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
      </button>

      <div class="collapse navbar-collapse" id="navbarSupportedContent">
          <ul class="navbar-nav mr-auto">
              {% for link in linklists[section.settings.menu].links %}
                {% if link.links != blank %}
                  <li class="nav-item dropdown">
                    <a href="{{ link.url }}" class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button"  data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                      {{ link.title }}
                     
                    </a>
                    <div class="dropdown-menu" aria-labelledby="navbarDropdown">
                      {% for childlink in link.links %}
                          <a href="{{ childlink.url }}" class="dropdown-item">
                            {{ childlink.title }}
                          </a>
                      {% endfor %}
                    </div>
                  </li>
                {% else %}
                  <li  class="nav-item">
                    <a href="{{ link.url }}" class="nav-link">
                      {{ link.title }}
                    </a>
                  </li>
                {% endif %}
              {% endfor %}
            </ul>
      </div>
      
  </nav>

How to add an "active" class to this navbar?