tsrman.github.io/Leaflet.groupedlayercontrol/example/exampledata.js

(function() {

  var basemaps = {
    Grayscale: L.tileLayer('http://{s}.tiles.wmflabs.org/bw-mapnik/{z}/{x}/{y}.png', {
      maxZoom: 18,
      attribution: '&copy; <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a>'
    }),
    Streets: L.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
      maxZoom: 19,
      attribution: '&copy; <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a>'
    })
  };

  var groups = {
    cities: new L.LayerGroup(),
    restaurants: new L.LayerGroup(),
    dogs: new L.LayerGroup(),
    cats: new L.LayerGroup()
  };

  L.marker([39.61, -105.02]).bindPopup('Littleton, CO.').addTo(groups.cities);
  L.marker([39.74, -104.99]).bindPopup('Denver, CO.').addTo(groups.cities);
  L.marker([39.73, -104.8]).bindPopup('Aurora, CO.').addTo(groups.cities);
  L.marker([39.77, -105.23]).bindPopup('Golden, CO.').addTo(groups.cities);

  L.marker([39.69, -104.85]).bindPopup('A restaurant').addTo(groups.restaurants);
  L.marker([39.69, -105.12]).bindPopup('A restaurant').addTo(groups.restaurants);

  L.marker([39.79, -104.95]).bindPopup('A dog').addTo(groups.dogs);
  L.marker([39.79, -105.22]).bindPopup('A dog').addTo(groups.dogs);

  L.marker([39.59, -104.75]).bindPopup('A cat').addTo(groups.cats);
  L.marker([39.59, -105.02]).bindPopup('A cat').addTo(groups.cats);

  window.ExampleData = {
    LayerGroups: groups,
    Basemaps: basemaps
  };

}());