Markers + popups. Enable Leaflet. Keep #map { height: 320px } in CSS.

Goal

Run every block and confirm the chart is visible.

<div id="map"></div>

#map { height: 320px; width: 100%; }

const map = L.map('map').setView([-1.0, 36.8], 6);
L.tileLayer('https://tile.openstreetmap.org/{z}/{x}/{y}.png', { attribution: '© OSM' }).addTo(map);
[['Nairobi',-1.29,36.82,21],['Mombasa',-4.04,39.67,15],['Kisumu',-0.09,34.77,15]].forEach(([n,lat,lng,u]) => L.marker([lat,lng]).addTo(map).bindPopup(n + ': ' + u + ' units'));
console.log('practice');

<div id="map"></div>

const map = L.map("map").setView([-1.29, 36.82], 6);
L.tileLayer("https://tile.openstreetmap.org/{z}/{x}/{y}.png", { attribution: "© OSM" }).addTo(map);
L.marker([-1.29, 36.82]).addTo(map);
console.log("marker");