ActionScript implements a couple of features that are not defined in ECMA-262 and some — but definitely not all — of ES4.
- Dynamically and statically typed code
- Packages, Classes and Interfaces
- Standard OO inheritance model (not prototype based, statically typed)
- uint and int datatype
- E4X (ECMA-357)
- Type-safe conditional compilation (ES4)
- Vector.<T> datatype (ES4)
Maybe I have forgotten some features. I am not sure if XML, XMLList etc. are already defined in 262 or came with 357.