У вас есть два варианта:
создать MarkerClusterer в функции addMarker (создать необходимый массив markers при создании маркеров).
создайте MarkerClusterer в функции initMap, добавьте каждый маркер к нему при его создании.
Пример в документации делаетэто первый путь.
function addMarker() {
var markers = [];
for (var i = 0; i < markersOnMap.length; i++) {
var contentString = '<div id="content"><p>' + markersOnMap[i].placeName +
'</p></div>';
const marker = new google.maps.Marker({
position: markersOnMap[i].LatLng[0],
map: map
});
const infowindow = new google.maps.InfoWindow({
content: contentString,
maxWidth: 200
});
marker.addListener('click', function() {
closeOtherInfo();
infowindow.open(marker.get('map'), marker);
InforObj[0] = infowindow;
});
marker.addListener('mouseover', function() {
closeOtherInfo();
infowindow.open(marker.get('map'), marker);
InforObj[0] = infowindow;
});
markers.push(marker);
}
var markerCluster = new MarkerClusterer(map, markers, {
imagePath: 'https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m'
});
}
подтверждение концепции скрипта
фрагмент кода:
var map;
var InforObj = [];
// Add a marker clusterer to manage the markers.
var centerCords = {
lat: 16.058324,
lng: 108.277000
};
var markersOnMap = [{
placeName: ' <b>Ho-Chi-Minh City</b> <br>' +
'Ho Chi Minh City (commonly known as Saigon) is a city in southern Vietnam. <br>' +
'Famous for the pivotal role it played in' +
'the Vietnam War. Its also known for its French colonial landmarks,' +
'including Notre-Dame Cathedral, made entirely of materials imported from France,' +
'and the 19th-century Central Post Office. Food stalls line the city’s streets,' +
'especially around bustling Bến Thành Market.',
LatLng: [{
lat: 10.775844,
lng: 106.701756
}]
},
{
placeName: "<b>Grand Mercure Danang (Da Nang City)</b> <br>" +
'<b>Address:</b> Zone of the Villas of Green Island, Lot A1, Đà Nẵng 084511, Vietnam. <br>' +
'<b>Five Star Hotel</b> - ☆☆☆☆☆ ',
icon: 'pin.png',
LatLng: [{
lat: 16.048297,
lng: 108.226951
}]
},
{
placeName: '<b>Da Nang City</b> <br>' +
'Da Nang is a coastal city in central Vietnam known for its sandy beaches and history' +
'as a French colonial port. Its a popular base for visiting the inland <b>Bà Nà</b> hills' +
'to the west of the city. Here the hillside <b>Hải Vân</b> Pass has views of Da Nang Bay' +
'and the Marble Mountains. These 5 limestone outcrops are topped with pagodas and hide' +
'caves containing Buddhist shrines.',
LatLng: [{
lat: 16.068000,
lng: 108.212000
}]
},
{
placeName: "<b>Dalat Hôtel du Parc (Dalat City)</b> <br>" +
'<b>Address:</b> 15 Đường Trần Phú, Phường 3, Thành phố Đà Lạt, Lâm Đồng, Vietnam',
icon: 'pin.png',
LatLng: [{
lat: 11.9367,
lng: 108.4390
}]
},
{
placeName: "<b>Nhà gỗ - The Wooden House Restaurant (Dalat City)</b> <br>" +
'<b>Address:</b> 26 Đường Nguyễn Đình Chiểu, Phường 9, Thành phố Đà Lạt, Lâm Đồng, Vietnam',
icon: 'pin.png',
LatLng: [{
lat: 11.9505,
lng: 108.4582
}]
},
{
placeName: '<b>Dalat City</b> <br>' +
'<b>Đà Lạt</b>, the capital of <b>Lâm Đồng</b> Province in southern Vietnam’s Central Highlands,' +
'is centered around a lake and golf course, and surrounded by hills, pine forests,' +
'lakes and waterfalls. Known as the “City of Eternal Spring” for its distinctive temperate' +
'climate, Đà Lạt was developed as a resort by the French in the early 1900s,' +
'and many reminders of its colonial heritage remain.',
LatLng: [{
lat: 11.936230,
lng: 108.445259
}]
},
{
placeName: "<b>Beaulieu Boutique Hotel (Hue City)</b> <br>" +
'<b>Address:</b> 15 Pham Ngu Lao, Hue, Vietnam',
icon: 'pin.png',
LatLng: [{
lat: 16.4691,
lng: 107.5947
}]
},
{
placeName: "<b>Hanh Restaurant (Hue City)</b> <br>" +
'<b>Address:</b> 11 Đường Phó Đức Chính, Phú Hội, Tp. Huế, Phú Hội, Vietnam',
icon: 'pin.png',
LatLng: [{
lat: 16.4663,
lng: 107.5950
}]
},
{
placeName: '<b>Hue City</b> <br>' +
'Huế is a city in central Vietnam that was the seat of Nguyen Dynasty emperors and the' +
'national capital from 1802 to 1945. A major attraction is its vast,' +
'19th-century <b>Đại Nội Citadel</b>, surrounded by a moat and thick stone walls.' +
'It encompasses the Imperial City, with palaces and shrines;' +
'the Forbidden Purple City (<b>Tử cấm thành</b>), once the emperor’s home;' +
'and a replica of the Royal Theater.',
LatLng: [{
lat: 16.463713,
lng: 107.590866
}]
},
{
placeName: "Vietnam (Hanoi Cooking Centre)",
icon: 'pin.png',
LatLng: [{
lat: 21.054374,
lng: 105.837032
}]
},
{
placeName: "Vietnam (Fortuna Hotel, Hanoi)",
icon: 'pin.png',
LatLng: [{
lat: 21.0215,
lng: 105.8178
}]
},
{
placeName: '<b>Hanoi</b> (<b>Capital City</b>) <br>' +
'is known for its centuries-old architecture and a rich culture with Southeast Asian,' +
'Chinese and French influences. At its heart is the chaotic Old Quarter, where the narrow' +
'streets are roughly arranged by trade. There are many little temples,' +
'including Bach Ma, honoring a legendary horse,' +
'plus Đồng Xuân Market, selling household goods and street food.',
LatLng: [{
lat: 21.027763,
lng: 105.834160
}]
}
];
window.onload = function() {
initMap();
};
function addMarker() {
var markers = [];
for (var i = 0; i < markersOnMap.length; i++) {
var contentString = '<div id="content"><p>' + markersOnMap[i].placeName +
'</p></div>';
const marker = new google.maps.Marker({
position: markersOnMap[i].LatLng[0],
map: map
});
const infowindow = new google.maps.InfoWindow({
content: contentString,
maxWidth: 200
});
marker.addListener('click', function() {
closeOtherInfo();
infowindow.open(marker.get('map'), marker);
InforObj[0] = infowindow;
});
marker.addListener('mouseover', function() {
closeOtherInfo();
infowindow.open(marker.get('map'), marker);
InforObj[0] = infowindow;
});
// marker.addListener('mouseout', function () {
// closeOtherInfo();
// infowindow.close();
// InforObj[0] = infowindow;
// });
markers.push(marker);
}
var markerCluster = new MarkerClusterer(map, markers, {
imagePath: 'https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m'
});
}
function closeOtherInfo() {
if (InforObj.length > 0) {
/* detach the info-window from the marker ... undocumented in the API docs */
InforObj[0].set("marker", null);
/* and close it */
InforObj[0].close();
/* blank the array */
InforObj.length = 0;
}
}
function initMap() {
map = new google.maps.Map(document.getElementById('map'), {
zoom: 4,
center: centerCords
});
addMarker();
}
html,
body, #map {
height: 100%;
margin: 0;
padding: 0;
}
<div id="map"></div>
<!-- Replace the value of the key parameter with your own API key. -->
<script async defer src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk&callback=initMap">
</script>
<script src="https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/markerclusterer.js"></script>