text: (function() {
  
      var thunderforestAttributions = [
          new ol.Attribution({
              html: 'Tiles &copy; <a href="http://www.thunderforest.com/">Thunderforest</a>'
          }),
          ol.source.OSM.ATTRIBUTION
      ];
  
      var map = new ol.Map({
          target: 'map',
          layers: [
              new ol.layer.Group({
                  'title': 'Base maps',
                  layers: [
                      new ol.layer.Tile({
                          title: 'Stamen - Water color',
                          type: 'base',
                          visible: false,
                          source: new ol.source.Stamen({
                              layer: 'watercolor'
                          })
                      }),
                      new ol.layer.Tile({
                          title: 'Stamen - Toner',
                          type: 'base',
                          visible: false,
                          source: new ol.source.Stamen({
                              layer: 'toner'
                          })
                      }),
                      new ol.layer.Tile({
                          title: 'Thunderforest - OpenCycleMap',
                          type: 'base',
                          visible: false,
                          source: new ol.source.OSM({
                              url: 'http://{a-c}.tile.thunderforest.com/cycle/{z}/{x}/{y}.png',
                              attributions: thunderforestAttributions
                          })
                      }),
                      new ol.layer.Tile({
                          title: 'Thunderforest - Outdoors',
                          type: 'base',
                          visible: false,
                          source: new ol.source.OSM({
                              url: 'http://{a-c}.tile.thunderforest.com/outdoors/{z}/{x}/{y}.png',
                              attributions: thunderforestAttributions
                          })
                      }),
                      new ol.layer.Tile({
                          title: 'Thunderforest - Landscape',
                          type: 'base',
                          visible: false,
                          source: new ol.source.OSM({
                              url: 'http://{a-c}.tile.thunderforest.com/landscape/{z}/{x}/{y}.png',
                              attributions: thunderforestAttributions
                          })
                      }),
                      new ol.layer.Tile({
                          title: 'Thunderforest - Transport',
                          type: 'base',
                          visible: false,
                          source: new ol.source.OSM({
                              url: 'http://{a-c}.tile.thunderforest.com/transport/{z}/{x}/{y}.png',
                              attributions: thunderforestAttributions
                          })
                      }),
                      new ol.layer.Tile({
                          title: 'Thunderforest - Transport Dark',
                          type: 'base',
                          visible: false,
                          source: new ol.source.OSM({
                              url: 'http://{a-c}.tile.thunderforest.com/transport-dark/{z}/{x}/{y}.png',
                              attributions: thunderforestAttributions
                          })
                      }),
                      new ol.layer.Tile({
                          title: 'OSM',
                          type: 'base',
                          visible: true,
                          source: new ol.source.OSM()
                      })
                  ]
              }),
              new ol.layer.Group({
                  title: 'Overlays',
                  layers: [
                      new ol.layer.Image({
                          title: 'Countries',
                          source: new ol.source.ImageArcGISRest({
                              ratio: 1,
                              params: {'LAYERS': 'show:0'},
                              url: "https://ons-inspire.esriuk.com/arcgis/rest/services/Administrative_Boundaries/Countries_December_2016_Boundaries/MapServer"
                          })
                      })
                  ]
              })
          ],
          view: new ol.View({
              center: ol.proj.transform([-0.92, 52.96], 'EPSG:4326', 'EPSG:3857'),
              zoom: 6
          })
      });
  
      map.addControl(new ol.control.LayerSwitcher());
  
  })();
  