Actionscript

Action Script

ActionScript 2.0 Features
Introduced in Flash MX 2004 and Flash MX Professional 2004, ActionScript 2.0 is a major grammatical overhaul of ActionScript as it existed in Flash 5 and Flash MX (retroactively dubbed ActionScript 1.0). ActionScript 2.0 adds relatively little new runtime functionality to the language but radically improves object-oriented development in Flash by formalizing objected-oriented programming (OOP) syntax and methodology.
While ActionScript 1.0 could be used in an object-oriented way, it lacked a traditional, official vocabulary for creating classes and objects. ActionScript 2.0 adds syntactic support for traditional object-oriented features. For example, ActionScript 2.0 provides a class keyword for creating classes and an extends keyword for establishing inheritance. Those keywords were absent from ActionScript 1.0 (though it was still possible to create prototypical objects that could be used as classes). The traditional OOP syntax of ActionScript 2.0 makes the language quite familiar for programmers coming from other OOP languages such as Java and C++.
Most of the new OOP syntax in ActionScript 2.0 is based on the proposed ECMAScript 4 standard. Its specification is posted at:
www.mozilla.org/js/language/es4.
Here are some of the key features introduced in ActionScript 2.0. Don’t worry if these features are new to you; the remainder of the book covers them in detail:
  * The class statement, used to create formal classes. The class statement is covered in Chapter 4.
  * The extends keyword, used to establish inheritance. In ActionScript 1.0 inheritance was typically established using the prototype property but could also be established via the __proto__ property. Inheritance is covered in Chapter 6.
  * The interface statement, used to create Java-style interfaces (i.e., abstract datatypes). Classes provide implementations for interfaces using the implements keyword. ActionScript 1.0 did not support...