A Basic Fullscreen Map
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
<link rel="stylesheet" href="../assets/leaflet.css" />
<script src="../assets/leaflet.js"></script>
<style>
#map {position:absolute;top:0;bottom:0;left:0;width:100%;}
.leaflet-control-attribution.leaflet-control a {color: #7F9F7F;}
</style>
</head>
<body>
<div id='map'></div>
<script src="map.js"></script>
</body>
</html>
The Script and Resulting Map
var map = L.map('map', {zoomControl:false,attribution:false}).setView([39.1189,-82.5351], 13);
var OpenStreetMap_Mapnik = L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
attribution: '© OpenStreetMap'
}).addTo(map);