LayerJsonType:
| "ArcGISAnnotationLayer"
| "ArcGISFeatureLayer"
| "ArcGISImageServiceLayer"
| "ArcGISImageServiceVectorLayer"
| "ArcGISMapServiceLayer"
| "ArcGISSceneServiceLayer"
| "ArcGISStreamLayer"
| "ArcGISTiledElevationServiceLayer"
| "ArcGISTiledImageServiceLayer"
| "ArcGISTiledMapServiceLayer"
| "BingMapsAerial"
| "BingMapsHybrid"
| "BingMapsRoad"
| "BuildingSceneLayer"
| "CSV"
| "GeoJSON"
| "GeoRSS"
| "GroupLayer"
| "IntegratedMeshLayer"
| "KML"
| "MediaLayer"
| "OpenStreetMap"
| "PointCloudLayer"
| "RasterDataElevationLayer"
| "SubtypeGroupLayer"
| "VectorTileLayer"
| "WebTiledLayer"
| "WFS"
| "WMS"
Constants for the layerType property of service layers. This field and its possible values isn't officially documented by esri, however it's used in ArcGIS online web maps.