examples/add-class-to-current-elem-example.html

<!doctype html>
<html>
  <head>
    <title>No options on initialization example</title>
    <style>
      #slider-container { width:612px; height:612px; }
      .current-slide {
        border-top: 3px solid red;
      }
    </style>
  </head>
  <body>
    <div id="slider-container">
      <img class="current-slide" src="http://placekitten.com/g/612/612"/>
      <img src="https://picsum.photos/612/612"/>
      <img src="https://picsum.photos/612/612?random=1"/>
      <img src="https://picsum.photos/612/612?random=2"/>
    </div>
  </body>
  <script src="../dist/simpleslider.js"></script>
  <script>
    var container = document.getElementById('slider-container');
    var children = container.children;

    function onSlideChanged(prev, next) {
      children[prev].className = '';
      children[next].className = 'current-slide';
    }

    simpleslider.getSlider({
      container: container,
      children: children,
      onChange: onSlideChanged
    });
  </script>
</html>