Simple swipe example using mapwarper source

<!DOCTYPE html>
<html>
  <head>
    <style>
      body { margin:0; padding:0; }
      #map { position:absolute; top:0; bottom:0; width:100%; }
    </style>
    <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
    <script src='https://api.mapbox.com/mapbox.js/v2.4.0/mapbox.js'></script>
    <link href='https://api.mapbox.com/mapbox.js/v2.4.0/mapbox.css' rel='stylesheet' />
  </head>
<body>
<style>
.range {
  position:absolute;
  width:100%;
  }
.leaflet-top .leaflet-control-zoom {
  top:20px;
  }
</style>

var overlay = L.tileLayer('https://mapwarper.net/layers/tile/572/{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([44.48,-73.212], 16);

clip();

</script>
</body>
</html>

https://api.mapbox.com/mapbox.js/v2.4.0/mapbox.js