JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet/v1.0.0-rc.1/leaflet.css">
<script src="http://cdn.leafletjs.com/leaflet/v1.0.0-rc.1/leaflet.js"></script>
<div id="map"></div>

CSS

#map {
    height: 500px;
}

JavaScript

var map = L.map("map");
L.tileLayer("http://{s}.tile.osm.org/{z}/{x}/{y}.png").addTo(map);

map.setView([48.85, 2.35], 12);

var marker, popupContent;

for (var i = 0; i < 1; i += 1) {
	marker = L.marker([48.85, 2.35]).addTo(map);
  popupContent = document.createElement("img");
  popupContent.onload = function () {
  	marker.openPopup();
  };
  popupContent.src = "http://c4.staticflickr.com/1/691/21131215939_49601d06ef_b.jpg";
  //popupContent = '<img src="http://c4.staticflickr.com/1/691/21131215939_49601d06ef_b.jpg" />';
  marker.bindPopup(popupContent, {
  	maxWidth: "auto"
  });
}

marker.openPopup();