Customize Layer List Widget for ArcGIS Web App Builder

widget.js

      //begin grouping feature layers for rooms and labels
          
      if (this.map.itemId) {  
          LayerInfos.getInstance(this.map, this.map.itemInfo)  
          .then(lang.hitch(this, function(operLayerInfos) {  
            this.operLayerInfos = operLayerInfos;  
  
  
            //create feature collections (groups) from feature layers
              
            var firstFloorLabels = new esri.layers.FeatureLayer("http://services.arcgis.com/2DbqGRRQS9wbBetw/arcgis/rest/services/Pv03_Labels/FeatureServer/0");            
                firstFloorLabels.setDefinitionExpression("floor='1'");
                firstFloorLabels.title = "1st Floor Labels";
              
            var firstFloorRooms = new esri.layers.FeatureLayer("http://services.arcgis.com/2DbqGRRQS9wbBetw/arcgis/rest/services/SM_prototype_2_1/FeatureServer/0");
                firstFloorRooms.setDefinitionExpression("floor_key='01'")  
                firstFloorRooms.title = "1st Floor Rooms";  
            var firstFloorLayers = [firstFloorLabels, firstFloorRooms]; 
            this.operLayerInfos.addFeatureCollection(firstFloorLayers, "1st Floor"); 
              
            var secondFloorLabels = new esri.layers.FeatureLayer("http://services.arcgis.com/2DbqGRRQS9wbBetw/arcgis/rest/services/Pv03_Labels/FeatureServer/0");  
                secondFloorLabels.setDefinitionExpression("floor='2'");  
                secondFloorLabels.title = "2nd Floor Labels";
            var secondFloorRooms = new esri.layers.FeatureLayer("http://services.arcgis.com/2DbqGRRQS9wbBetw/arcgis/rest/services/SM_prototype_2_1/FeatureServer/0");
                secondFloorRooms.setDefinitionExpression("floor_key='02'")
                secondFloorRooms.title = "2nd Floor Rooms";                
            var secondFloorLayers = [secondFloorLabels, secondFloorRooms];               
            this.operLayerInfos.addFeatureCollection(secondFloorLayers, "2nd Floor");                             
            
            var thirdFloorLabels = new esri.layers.FeatureLayer("http://services.arcgis.com/2DbqGRRQS9wbBetw/arcgis/rest/services/Pv03_Labels/FeatureServer/0");  
                thirdFloorLabels.setDefinitionExpression("floor='3'");
                thirdFloorLabels.title = "3rd Floor Labels";              
            var thirdFloorRooms = new esri.layers.FeatureLayer("http://services.arcgis.com/2DbqGRRQS9wbBetw/arcgis/rest/services/SM_prototype_2_1/FeatureServer/0");
                thirdFloorRooms.setDefinitionExpression("floor='3'");
                thirdFloorRooms.title = "3rd Floor Rooms";                
            var thirdFloorLayers = [thirdFloorLabels, thirdFloorRooms];                
            this.operLayerInfos.addFeatureCollection(thirdFloorLayers, "3rd Floor");  
              

            //this.showLayers();  
            //this.bindEvents();  
            this.own(on(this.operLayerInfos,  
                        'layerInfosChanged',  
                        lang.hitch(this, this._onLayerInfosChanged)));  
            dom.setSelectable(this.layersSection, false);  
          }));  
        } else {  
          var itemInfo = this._obtainMapLayers();  
          LayerInfos.getInstance(this.map, itemInfo)  
          .then(lang.hitch(this, function(operLayerInfos) {  
            this.operLayerInfos = operLayerInfos;  
            //this.showLayers();  
            //this.bindEvents();  
            this.own(on(this.operLayerInfos,  
                        'layerInfosChanged',  
                        lang.hitch(this, this._onLayerInfosChanged)));  
            dom.setSelectable(this.layersSection, false);  
          }));  
        } 
      // end of code to group layers  
          
      }