var tileLayer = new L.TileLayer('https://stamen-tiles.a.ssl.fastly.net/terrain/{z}/{x}/{y}.png',{
  attribution: '&copy; <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors, &copy; <a href="http://cartodb.com/attributions">CartoDB</a>'
});

var map = new L.Map('map', {
  'center': [37.235905, -113.407354],
  'zoom': 10,
  'layers': [tileLayer]
});

var marker = L.marker([37.235905, -113.407354],{
  draggable: true
}).addTo(map);

marker.on('dragend', function (e) {
  document.getElementById('lat').value = marker.getLatLng().lat;
  document.getElementById('lon').value = marker.getLatLng().lng;
});