index.html
<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Swipe between layers</title>
<meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
<script src='//cdn.leafletjs.com/leaflet-0.7.3/leaflet.js'></script>
<link rel="stylesheet" href="//cdn.leafletjs.com/leaflet-0.7.3/leaflet.css" />
<style>
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
</style>
</head>
<body>
<style>
.range {
position:absolute;
width:100%;
}
.leaflet-top .leaflet-control-zoom {
top:20px;
}
</style>
<div id='map'></div>
<input id='range' class='range' type='range' min='0' max='1.0' step='any' />
<script>
var map = L.map('map');
L.tileLayer('//tile.stamen.com/watercolor/{z}/{x}/{y}.png').addTo(map);
var overlay = L.tileLayer('//a.tile.thunderforest.com/cycle/{z}/{x}/{y}.png').addTo(map);
var range = document.getElementById('range');
function clip() {
var nw = map.containerPointToLayerPoint([0, 0]),
se = map.containerPointToLayerPoint(map.getSize()),
clipX = nw.x + (se.x - nw.x) * range.value;
overlay.getContainer().style.clip = 'rect(' + [nw.y, clipX, se.y, nw.x].join('px,') + 'px)';
}
range['oninput' in range ? 'oninput' : 'onchange'] = clip;
map.on('move', clip);
map.setView([41.38506, 2.17340], 15);
clip();
</script>
</body>
</html>