Google Maps Marker Clustering not working

I got this code from this Snippet here that works fine and changed a little bit. But now I wanted to add Marker Clustering to the map like this but I get nothing to work. I added

<script src="https://unpkg.com/@google/markerclustererplus@4.0.1/dist/markerclustererplus.min.js"></script>

to the head and

var markerCluster = new MarkerClusterer(markers1,
{imagePath:'https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m'});

in front of “markers1 =” but then I get the error

Uncaught TypeError: e.getDraggable is not a function

I don’t know why this code is not working here without the marker cluster. On my Page, it works fine.

var gmarkers1 = [];
var markers1 = [];
var infowindow = new google.maps.InfoWindow({
    content: ''
});

// Our markers
markers1 = [
      ["0", "***", ***, ***, "1", "red", "-35", "<h3>***<span style='font-size: 10pt;'>( 12345)</span></h3>"],
      ];


/**
 * Function to init map
 */

function initialize() {
    var center = new google.maps.LatLng(52.4357808, 4.991315699999973);
    var mapOptions = {
        zoom: 6,
        clickableIcons: false,
        center: {lat: 50.533481, lng: 10.018343},
        disableDefaultUI: true,
        streetViewControl: false,
        zoomControl: true,
        gestureHandling: 'greedy',
        zoomControlOptions: {
          style: google.maps.ZoomControlStyle.SMALL,
          position: google.maps.ControlPosition.RIGHT
        },
      };

    map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions);
    for (i = 0; i < markers1.length; i++) {
        addMarker(markers1[i]);
    }
}

/**
 * Function to add marker to map
 */

function addMarker(marker) {
    var category = marker[4];
    var title = marker[1];
    var color = marker[5];
    var pos = new google.maps.LatLng(marker[2], marker[3]);
    var content = marker[7];
    var rotations = marker[6];

    var icon = {
        path: "M320.69 630.86C320.69 630.86 520.91 323.43 520.91 222.4C520.91 73.71 419.43 9.03 320.46 8.8C221.49 9.03 120 73.71 120 222.4C120 323.43 320.34 630.86 320.34 630.86C320.34 630.86 320.46 630.51 320.46 630.51C320.46 630.63 320.64 630.79 320.69 630.86ZM320.57 144.46C358.97 144.46 390.06 175.54 390.06 213.94C390.06 252.34 358.86 283.43 320.46 283.43C282.17 283.43 251.09 252.34 251.09 213.94C251.09 175.54 282.17 144.46 320.57 144.46Z", //SVG path of awesomefont marker
        fillColor: color, //color of the marker
        fillOpacity: 1,
        strokeWeight: 0,
        rotation:parseInt(rotations),
        scale: 0.06, //size of the marker, careful! this scale also affects anchor and labelOrigin
        anchor: new google.maps.Point(310,620), //position of the icon, careful! this is affected by scale
        labelOrigin: new google.maps.Point(205,190) //position of the label, careful! this is affected by scale
    }
    marker1 = new google.maps.Marker({
        title: title,
        position: pos,
        category: category,
        map: map,
        icon:icon
    });
    

        

    gmarkers1.push(marker1);

    // Marker click listener
    google.maps.event.addListener(marker1, 'click', (function (marker1, content) {
        return function () {
            infowindow.setContent(content);
            infowindow.open(map, marker1);
            map.panTo(this.getPosition());
        }
    })(marker1, content));
}
var markerCluster = new MarkerClusterer(markers1, {imagePath:'https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m'});
filterMarkers = function (category) {
    for (i = 0; i < gmarkers1.length; i++) {
        marker = gmarkers1[i];
        // If is same category or category not picked
        if (marker.category == category || category.length === 0) {
        //Close InfoWindows
            marker.setVisible(true);
                        if (infowindow) {
                infowindow.close();
            }
        }
        // Categories don't match 
        else {
            marker.setVisible(false);
        }
    }
}

// Init map
initialize();

#map-canvas {
    width: 100%;
    height: 100%;
}

<head>
<script src="https://maps.googleapis.com/maps/api/js?"></script>
<script src="https://unpkg.com/@google/markerclustererplus@4.0.1/dist/markerclustererplus.min.js"></script>
</head>
<body>
<div id="map-canvas" style="position: relative; overflow: hidden;"></div>
<select id="type" onchange="filterMarkers(this.value);">
    <option value="">***</option>
    <option value="1">***</option>
    <option value="2">***</option>
    <option value="3">***</option>
    <option value="4">***</option>
</select>
</body>

Answer

When I add the specified code to the posted code snippet:

1. <script src="https://unpkg.com/@google/markerclustererplus@4.0.1/dist/markerclustererplus.min.js"></script> to the head
2. var markerCluster = new MarkerClusterer(gmarkers1, {imagePath:'https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m'}); to after the gmarkers1 array is available (after the loop calling addMarker(markers1[i]);

I get the javascript error you report: Uncaught TypeError: e.getDraggable is not a function

That is because the constructor takes three arguments:

var markerCluster = new MarkerClusterer(map, markers,
       {imagePath: 'https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m'});

(your are missing the first map argument)

Update

two additional issues with the updated code in your question:

1. the MarkerClusterer constructor is in the wrong place (it is outside the initialize function, it runs before the markers are created.
2. the markers1 array is the wrong type to add to the MarkerClusterer, they need to be google.maps.Marker objects (the gmarkers1 array)

working code snippet:

var gmarkers1 = [];
var markers1 = [];
var infowindow = new google.maps.InfoWindow({
  content: ''
});

// Our markers
markers1 = [
  ["0", "Leichlingen", 51.106277, 7.018726, "1", "red", "-35", "<h3>Leichlingen <span style='font-size: 10pt;'>( 42799 )</span></h3><p>Internet: 0 (0%)<p>Social Media: 0 (0%)<p>Dein HSK: 0 (0%)<p>Newsletter: 0 (0%)<p>Banner:  (0%)<p>Zeitung: 0 (0%)<p>Bus: 0 (0%)<p>Radio: 0 (0%)<p>Hören Sagen: 0 (0%)<p>vor Ort:  (0%)<p>Sonstiges: 1 (100%)"],
  ["1", "Stuttgart", 48.7667, 9.18333, "1", "red", "-35", "<h3>Stuttgart <span style='font-size: 10pt;'>( 70327 )</span></h3><p>Internet: 0 (0%)<p>Social Media: 0 (0%)<p>Dein HSK: 0 (0%)<p>Newsletter: 0 (0%)<p>Banner:  (0%)<p>Zeitung: 0 (0%)<p>Bus: 0 (0%)<p>Radio: 0 (0%)<p>Hören Sagen: 1 (100%)<p>vor Ort:  (0%)<p>Sonstiges: 0 (0%)"],
  ["2", "Pfaffenhofen", 49.0644444, 8.9763889, "1", "red", "-35", "<h3>Pfaffenhofen <span style='font-size: 10pt;'>( 74397 )</span></h3><p>Internet: 0 (0%)<p>Social Media: 0 (0%)<p>Dein HSK: 0 (0%)<p>Newsletter: 0 (0%)<p>Banner:  (0%)<p>Zeitung: 0 (0%)<p>Bus: 0 (0%)<p>Radio: 0 (0%)<p>Hören Sagen: 1 (100%)<p>vor Ort:  (0%)<p>Sonstiges: 0 (0%)"],
  ["3", "Bretten", 49.03685, 8.707453, "1", "red", "-35", "<h3>Bretten <span style='font-size: 10pt;'>( 75015 )</span></h3><p>Internet: 0 (0%)<p>Social Media: 2 (13%)<p>Dein HSK: 0 (0%)<p>Newsletter: 0 (0%)<p>Banner:  (0%)<p>Zeitung: 4 (27%)<p>Bus: 4 (27%)<p>Radio: 0 (0%)<p>Hören Sagen: 3 (20%)<p>vor Ort:  (0%)<p>Sonstiges: 2 (13%)"],
  ["4", "Oberderdingen", 49.0655556, 8.8030556, "1", "red", "-35", "<h3>Oberderdingen <span style='font-size: 10pt;'>( 75038 )</span></h3><p>Internet: 0 (0%)<p>Social Media: 0 (0%)<p>Dein HSK: 0 (0%)<p>Newsletter: 0 (0%)<p>Banner:  (0%)<p>Zeitung: 3 (19%)<p>Bus: 1 (6%)<p>Radio: 0 (0%)<p>Hören Sagen: 7 (44%)<p>vor Ort:  (0%)<p>Sonstiges: 4 (25%)"],
];


/**
 * Function to init map
 */

function initialize() {
  var center = new google.maps.LatLng(52.4357808, 4.991315699999973);
  var mapOptions = {
    zoom: 6,
    clickableIcons: false,
    center: {
      lat: 50.533481,
      lng: 10.018343
    },
    disableDefaultUI: true,
    streetViewControl: false,
    zoomControl: true,
    gestureHandling: 'greedy',
    zoomControlOptions: {
      style: google.maps.ZoomControlStyle.SMALL,
      position: google.maps.ControlPosition.RIGHT
    },
  };

  map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions);
  
  for (i = 0; i < markers1.length; i++) {
    addMarker(markers1[i]);
  }
  var markerCluster = new MarkerClusterer(map, gmarkers1, {imagePath:'https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m'});
}

/**
 * Function to add marker to map
 */

function addMarker(marker) {
  var category = marker[4];
  var title = marker[1];
  var color = marker[5];
  var pos = new google.maps.LatLng(marker[2], marker[3]);
  var content = marker[7];
  var rotations = marker[6];

  var icon = {
    path: "M320.69 630.86C320.69 630.86 520.91 323.43 520.91 222.4C520.91 73.71 419.43 9.03 320.46 8.8C221.49 9.03 120 73.71 120 222.4C120 323.43 320.34 630.86 320.34 630.86C320.34 630.86 320.46 630.51 320.46 630.51C320.46 630.63 320.64 630.79 320.69 630.86ZM320.57 144.46C358.97 144.46 390.06 175.54 390.06 213.94C390.06 252.34 358.86 283.43 320.46 283.43C282.17 283.43 251.09 252.34 251.09 213.94C251.09 175.54 282.17 144.46 320.57 144.46Z", //SVG path of awesomefont marker
    fillColor: color, //color of the marker
    fillOpacity: 1,
    strokeWeight: 0,
    rotation: parseInt(rotations),
    scale: 0.06, //size of the marker, careful! this scale also affects anchor and labelOrigin
    anchor: new google.maps.Point(310, 620), //position of the icon, careful! this is affected by scale
    labelOrigin: new google.maps.Point(205, 190) //position of the label, careful! this is affected by scale
  }
  marker1 = new google.maps.Marker({
    title: title,
    position: pos,
    category: category,
    map: map,
    icon: icon
  });

  gmarkers1.push(marker1);

  // Marker click listener
  google.maps.event.addListener(marker1, 'click', (function(marker1, content) {
    return function() {
      infowindow.setContent(content);
      infowindow.open(map, marker1);
      map.panTo(this.getPosition());
    }
  })(marker1, content));
}
filterMarkers = function(category) {
  for (i = 0; i < gmarkers1.length; i++) {
    marker = gmarkers1[i];
    // If is same category or category not picked
    if (marker.category == category || category.length === 0) {
      //Close InfoWindows
      marker.setVisible(true);
      if (infowindow) {
        infowindow.close();
      }
    }
    // Categories don't match 
    else {
      marker.setVisible(false);
    }
  }
}

// Init map
initialize();

html,
body {
  width: 100%;
  height: 100%;
  padding: 0px;
  margin: 0px;
}

#map-canvas {
  width: 100%;
  height: 95%;
}

<head>
  <script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk"></script>
  <script src="https://unpkg.com/@google/markerclustererplus@4.0.1/dist/markerclustererplus.min.js"></script>
</head>

<body>
  <div id="map-canvas" style="position: relative; overflow: hidden;"></div>
  <select id="type" onchange="filterMarkers(this.value);">
    <option value="">***</option>
    <option value="1">***</option>
    <option value="2">***</option>
    <option value="3">***</option>
    <option value="4">***</option>
  </select>
</body>