Leaflet map marker clusters not showing icons

Question

I'm trying to make a map with leafletjs, but I can't get marker clusters to work properly. I'd like it to show the default icons for marker clustering, but instead it shows no marker cluster icons at all. Here's a demonstration:

var map = L.map('mapid').setView([51.505, -0.09], 13);

L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6ImNpejY4NXVycTA2emYycXBndHRqcmZ3N3gifQ.rJcFIG214AriISLbB6B5aw', {
  maxZoom: 18,
  attribution: 'Map data &copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, ' +
    '<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, ' +
    'Imagery © <a href="http://mapbox.com">Mapbox</a>',
  id: 'mapbox.streets'
}).addTo(map);

var markers = L.markerClusterGroup();
markers.addLayer(L.marker([51.505, -0.09]));
markers.addLayer(L.marker([51.506, -0.09]));
map.addLayer(markers);

<link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css" integrity="sha512-wcw6ts8Anuw10Mzh9Ytw4pylW8+NAD4ch3lqm9lzAsTxg0GFeJgoAtxuCLREZSC5lUXdVyo/7yfsqFjQ4S+aKw==" crossorigin="" />
<script src="https://unpkg.com/[email protected]/dist/leaflet.js" integrity="sha512-mNqn2Wg7tSToJhvHcqfzLMU6J4mkOImSPTxVZAdo+lcPlk+GhZmYgACEe0x35K7YzW1zJ7XyJV/TT1MrdXvMcA==" crossorigin=""></script>
<script src="https://leaflet.github.io/Leaflet.markercluster/dist/leaflet.markercluster-src.js"></script>
<div id="mapid" style="height:380px;"></div>

This code is completely based on the examples on http://leafletjs.com/examples/quick-start/ and https://github.com/Leaflet/Leaflet.markercluster#usage so I'd imagine it would work given those examples, but it doesn't seem like this actually shows the icons behind the clusters.

I have found that a markerClusterGroup has a method called _defaultIconCreateFunction, but it doesn't seem to get called (or if it does get called, it doesn't do anything).

So what am I doing wrong here?

Answer 1

You also need MarkerCluster.css and MarkerCluster.Default.css

var map = L.map('mapid').setView([51.505, -0.09], 13);

L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6ImNpejY4NXVycTA2emYycXBndHRqcmZ3N3gifQ.rJcFIG214AriISLbB6B5aw', {
  maxZoom: 18,
  attribution: 'Map data &copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, ' +
    '<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, ' +
    'Imagery © <a href="http://mapbox.com">Mapbox</a>',
  id: 'mapbox.streets'
}).addTo(map);

var markers = L.markerClusterGroup();
markers.addLayer(L.marker([51.505, -0.09]));
markers.addLayer(L.marker([51.506, -0.09]));
map.addLayer(markers);

<link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css" integrity="sha512-wcw6ts8Anuw10Mzh9Ytw4pylW8+NAD4ch3lqm9lzAsTxg0GFeJgoAtxuCLREZSC5lUXdVyo/7yfsqFjQ4S+aKw==" crossorigin="" />
<script src="https://unpkg.com/[email protected]/dist/leaflet.js" integrity="sha512-mNqn2Wg7tSToJhvHcqfzLMU6J4mkOImSPTxVZAdo+lcPlk+GhZmYgACEe0x35K7YzW1zJ7XyJV/TT1MrdXvMcA==" crossorigin=""></script>

<link rel="stylesheet" href="https://leaflet.github.io/Leaflet.markercluster/dist/MarkerCluster.css" />
<link rel="stylesheet" href="https://leaflet.github.io/Leaflet.markercluster/dist/MarkerCluster.Default.css" />
<script src="https://leaflet.github.io/Leaflet.markercluster/dist/leaflet.markercluster-src.js"></script>
<div id="mapid" style="height:380px;"></div>