examples/collapse-groups.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>OpenLayers - LayerSwitcher</title>
    <meta
      name="viewport"
      content="initial-scale=1.0, user-scalable=no, width=device-width"
    />
    <link
      rel="stylesheet"
      href="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@main/dist/en/v7.0.0/legacy/ol.css"
    />
    <link rel="stylesheet" href="../dist/ol-layerswitcher.css" />
    <link rel="stylesheet" href="layerswitcher.css" />
  </head>
  <body>
    <div id="map"></div>
    <script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@main/dist/en/v7.0.0/legacy/ol.js"></script>
    <script src="../dist/ol-layerswitcher.js"></script>
    <script src="collapse-groups.js"></script>
  </body>
</html>