OpenLayers change cluster style

by barbarina

HTML

<script src="https://openlayers.org/en/latest/build/ol.js"></script>
<link rel="stylesheet" href="https://openlayers.org/en/latest/css/ol.css">
<link rel="stylesheet" href="https://viglino.github.io/ol-ext/dist/ol-ext.css">
<script src="https://viglino.github.io/ol-ext/dist/ol-ext.js"></script>
<div id="map" class="map">

</div>

CSS

.map {
  height: 300px;
  width: 100%;
}

JavaScript

const MARKER_SIZE = 25;

const geojsonObject = {
    'type': 'FeatureCollection',
    'crs': {
        'type': 'name',
        'properties': {
            'name': 'EPSG:4326',
        },
    },
    'features': [{
        'type': 'Feature',
        'geometry': {
            'type': 'Point',
            'coordinates': [10, 10]
        },'properties': {'nome': 'a'}
    }, {
        'type': 'Feature',
        'geometry': {
            'type': 'Point',
            'coordinates': [10, 10]
        },'properties': {'nome': 'b'}
    }, {
        'type': 'Feature',
        'geometry': {
            'type': 'Point',
            'coordinates': [10.4, 10.4]
        },'properties': {'nome': 'c'}
    }, {
        'type': 'Feature',
        'geometry': {
            'type': 'Point',
            'coordinates': [10.4, 10.4]
        },'properties': {'nome': 'd'}
    }, {
        'type': 'Feature',
        'geometry': {
            'type': 'Point',
            'coordinates': [10.4, 10.4]
        },'properties': {'nome': 'e'}
    }, {
        'type': 'Feature',
        'geometry': {
            'type': 'Point',
            'coordinates': [10.5, 10.5]
        },'properties': {'nome': 'f'}
    }, {
        'type': 'Feature',
        'geometry': {
            'type': 'Point',
            'coordinates': [10.5, 10.5]
        },'properties': {'nome': 'g'}
    }]
};


const raster = new ol.layer.Tile({
  source: new ol.source.Stamen({
    layer: 'toner-lite',
  }),
});

const getShadowStyle = () => {
    return new ol.style.Style({
        image: new ol.style.Shadow({
            radius: MARKER_SIZE,
            blur: 5,
            fill: new ol.style.Fill({
                color: 'rgba(0, 0, 0, 0.5)',
            })
        })
    });
};

const getPoiStyle = (feature, extraDefs = {}) => {
    const features = feature.get('features');
    let color = '#255CF6';
    let glyph = 'icomoon-bike';

    return new ol.style.Style(
        Object.assign({}, {
                image: new...