Source

<!DOCTYPE html>
<html>
  <head>
    <title>Make the map use the full window</title>
    <meta charset="utf-8" />
    <script src="../../bower_components/leaflet/dist/leaflet.js"></script>
    <link rel="stylesheet" href="../../bower_components/leaflet/dist/leaflet.css"/>
    <script src="../../bower_components/leaflet-providers/leaflet-providers.js"></script>
    <style>
      body {
        margin: 0;
        padding: 0;
      }
      #mapDiv {
        position: absolute;
        top: 0;
        bottom: 0;
        width: 100%;
      }
    </style>
  </head>
  <body>
    <div id='mapDiv'></div>
    <script>
      var latLon = [53.56250, 9.95982];
      var zoom = 18;

      var osmLayer = L.tileLayer.provider('OpenStreetMap.Mapnik');

      var myMap = L.map('mapDiv', { layers: osmLayer}).setView(latLon, zoom);
    </script>
  </body>
</html>