JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.6.2/leaflet.css">
<script src="http://cdn.leafletjs.com/leaflet-0.6.2/leaflet.js"></script>
 <div id="map"></div>

CSS

#map { height: 400px; }

JavaScript

var map = L.map('map').setView([51.505, -0.09], 10);
L.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
    maxZoom: 18
}).addTo(map);

customCircleMarker = L.CircleMarker.extend({
   options: { 
      someCustomProperty: 'Custom data!',
      anotherCustomProperty: 'More data!'
   }
});

var myMarker = new customCircleMarker([51.505, -0.09], { 
    title: 'Marker',
    radius: 20,
    someCustomProperty: 'Adding custom data to this marker!',
    anotherCustomProperty: 'More custom data to this marker!'
});
myMarker.addTo(map);