preview.html

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Map Preview</title>
    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.3.4/dist/leaflet.css" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.3.4/leaflet.js"></script>
    <script type="text/javascript" src="preview/leaflet-hash.js"></script>
  </head>

  <body style="margin: 0">
    <div id="mapid" style="width: 100vw; height: 100vh"></div>
    <script>
      const mymap = L.map("mapid").setView([49, 20], 10);
      L.tileLayer("http://localhost:4000/{z}/{x}/{y}", {
        maxZoom: 18,
        attribution: 'Map data &copy; <a href="https://www.openstreetmap.org/">OpenStreetMap</a> contributors',
      }).addTo(mymap);
      new L.Hash(mymap);
    </script>
  </body>
</html>