index.js

function initMap() {
    const map = new google.maps.Map(document.getElementById("map"), {
      zoom: 3,
      center: { lat: -28.024, lng: 140.887 },
    });
    const infoWindow = new google.maps.InfoWindow({
      content: "",
      disableAutoPan: true,
    });
    // Create an array of alphabetical characters used to label the markers.
    const labels = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    // Add some markers to the map.
    const markers = locations.map((position, i) => {
      const label = labels[i % labels.length];
      const marker = new google.maps.Marker({
        position,
        label,
        map: map,
      });
  
      // markers can only be keyboard focusable when they have click listeners
      // open info window when marker is clicked
      marker.addListener("click", () => {
        infoWindow.setContent(label);
        infoWindow.open(map, marker);
      });
      return marker;
    });
  
    // Add a marker clusterer to manage the markers.
    const markerCluster = new MarkerClusterer({ map, markers });
  }
  
const locations = [
    { lat: -31.56391, lng: 147.154312 },
    { lat: -33.718234, lng: 150.363181 },
    { lat: -33.727111, lng: 150.371124 },
    { lat: -33.848588, lng: 151.209834 },
    { lat: -33.851702, lng: 151.216968 },
    { lat: -34.671264, lng: 150.863657 },
    { lat: -35.304724, lng: 148.662905 },
    { lat: -36.817685, lng: 175.699196 },
    { lat: -36.828611, lng: 175.790222 },
    { lat: -37.75, lng: 145.116667 },
    { lat: -37.759859, lng: 145.128708 },
    { lat: -37.765015, lng: 145.133858 },
    { lat: -37.770104, lng: 145.143299 },
    { lat: -37.7737, lng: 145.145187 },
    { lat: -37.774785, lng: 145.137978 },
    { lat: -37.819616, lng: 144.968119 },
    { lat: -38.330766, lng: 144.695692 },
    { lat: -39.927193, lng: 175.053218 },
    { lat: -41.330162, lng: 174.865694 },
    { lat: -42.734358, lng: 147.439506 },
    { lat: -42.734358, lng: 147.501315 },
    { lat: -42.735258, lng: 147.438 },
    { lat: -43.999792, lng: 170.463352 },
];
  
window.initMap = initMap;