dist/samples/maxzoom-simple/inline.html

<!DOCTYPE html>
<html>
  <head>
    <title>Maximum Zoom Imagery Service</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <style type="text/css">
      /* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
      #map {
        height: 100%;
      }

      /* Optional: Makes the sample page fill the window. */
      html,
      body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
    </style>
    <script>
      let map;
      let maxZoomService;
      let infoWindow;

      function initMap() {
        map = new google.maps.Map(document.getElementById("map"), {
          zoom: 11,
          center: { lat: 35.6894, lng: 139.692 },
          mapTypeId: "hybrid",
        });
        infoWindow = new google.maps.InfoWindow();
        maxZoomService = new google.maps.MaxZoomService();
        map.addListener("click", showMaxZoom);
      }

      function showMaxZoom(e) {
        maxZoomService.getMaxZoomAtLatLng(e.latLng, (result) => {
          if (result.status !== "OK") {
            infoWindow.setContent("Error in MaxZoomService");
          } else {
            infoWindow.setContent(
              "The maximum zoom at this location is: " + result.zoom
            );
          }
          infoWindow.setPosition(e.latLng);
          infoWindow.open(map);
        });
      }
    </script>
  </head>
  <body>
    <div id="map"></div>

    <!-- Async script executes immediately and must be after any DOM elements used in callback. -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap&libraries=&v=weekly"
      async
    ></script>
  </body>
</html>