Using the layer classes

You can use the various layer classes in the API for JavaScript to reference map services hosted by ArcGIS Server and other map servers. All layer classes inherit from the Layer base class. The Layer class has no constructor so you can't create an actual object instance from this class. This base class simply defines properties, methods, and events that must exist in all classes that inherit from it:

As indicated in the preceding figure, DynamicMapServiceLayer, TiledMapServiceLayer, and GraphicsLayer all inherit directly from the Layer class. (Note that there are several other layers that inherit from Layer, but many of those are for special use cases, so our diagram shows only these more commonly-used classes.)

DynamicMapServiceLayer and TiledMapserviceLayer also act as base classes. DynamicMapServiceLayer is the base class for dynamic map services while TiledMapServiceLayer is the base class for tiled map services. Layer, DynamicMapServiceLayer, and TiledMapServiceLayer are all base classes meaning that you can't specifically create an object from these classes in your application.