Cesiumjs interface

Cesium.Appearance is a superclass or interface for other Appearance like EllipsoidSurfaceAppearance.
my questions is
why does cesium.js use extends of javascript grammar between them?

Looking forward to your reply.

Hi @zxc1987,

Apologies for the delayed response. Cesium does not use the class or extends keywords to declare its classes; instead, these are created by defining constructor functions. You can read more about how Cesium writes its code through the Coding Guide below.

Let me know if I can help with anything else!