JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-1.0.0-b1/leaflet.css">
<script src="http://cdn.leafletjs.com/leaflet-1.0.0-b1/leaflet.js"></script>
<script src="https://rawgit.com/Leaflet/Leaflet.markercluster/leaflet-master/dist/leaflet.markercluster-src.js"></script>
<div id="map">
    
</div>

CSS

#map{
    height:500px;
    width:500px;
}

JavaScript

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

		L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6IjZjNmRjNzk3ZmE2MTcwOTEwMGY0MzU3YjUzOWFmNWZhIn0.Y8bhBaUMqFiPrDRW9hieoQ', {
			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);


		L.marker([51.5, -0.09]).addTo(map)
			.bindPopup("<b>Hello world!</b><br />I am a popup.").openPopup();

		L.circle([51.508, -0.11], 500, {
			color: 'red',
			fillColor: '#f03',
			fillOpacity: 0.5
		}).addTo(map).bindPopup("I am a circle.");

		L.polygon([
			[51.509, -0.08],
			[51.503, -0.06],
			[51.51, -0.047]
		]).addTo(map).bindPopup("I am a polygon.");
	L.polygon([
			[52.509, -1.08],
			[52.503, -1.06],
			[52.51, -1.047]
		]).addTo(map).bindPopup("I am a polygon.");
    	L.polygon([
			[53.509, -2.08],
			[53.503, -2.06],
			[53.51, -2.047]
		]).addTo(map).bindPopup("I am a polygon.");
    	L.polygon([
			[54.509, -3.08],
			[54.503, -3.06],
			[54.51, -3.047]
		]).addTo(map).bindPopup("I am a polygon.");
    	L.polygon([
			[55.509, -4.08],
			[55.503, -4.06],
			[55.51, -4.047]
		]).addTo(map).bindPopup("I am a polygon.");

		var popup = L.popup();

		function onMapClick(e) {
			popup
				.setLatLng(e.latlng)
				.setContent("You clicked the map at " + e.latlng.toString())
				.openOn(map);
		}

		map.on('click', onMapClick);
        
//var markerClusterTest = new L.MarkerClusterGroup();
var markerClusterTest2 = L.markerClusterGroup();