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Học Actionscript 3.0 - p 5

CHAPTER 2 Core Language fundamentaLs ActionScript 3.0 is a complete rewrite of the language—so much so that ActionScript 3.0 doesn’t even share the same Flash Player code base as prior versions of ActionScript. But that’s all behind the scenes. The truth is that all versions of ActionScript to date have quite a bit in common. This is because ActionScript is based on a scripting language standard (called ECMA-262) that grew from the success of JavaScript, and ongoing versions of ActionScript are as backward-compatible as possible in an effort to support legacy projects. Of course, each new update to ActionScript introduces new features and,. | CHAPTER CORE LANGUAGE FUNDAMENTALS ActionScript 3.0 is a complete rewrite of the language so much so that ActionScript 3.0 doesn t even share the same Flash Player code base as prior versions of ActionScript. But that s all behind the scenes. The truth is that all versions of ActionScript to date have quite a bit in common. This is because ActionScript is based on a scripting language standard called ECMA-262 that grew from the success of JavaScript and ongoing versions of ActionScript are as backward-compatible as possible in an effort to support legacy projects. Of course each new update to ActionScript introduces new features and because the decision was made to create ActionScript 3.0 from scratch an oppor tunity presented itself to tidy up a few messy things that lingered from previous versions. Among these improvements are tightening up and requiring best practices that had been optional and restructuring how events and graphical assets are handled the Event Model and Display List respectively . All of this progress however didn t steamroll over the standard upon which ActionScript is based and most of the language fundamentals remain intact. With the intention to focus on new ActionScript 3.0 features later on we want to cover some of the more commonly used fundamentals up front. We do not intend to ignore these ideas throughout the rest of the book. However we hope to explain them in sufficient detail here and spend less time on them as we proceed. This book doesn t assume that you re well versed in any prior version of ActionScript but its size and purpose requires that we assume a basic understanding of general scripting concepts. If you haven t already please look over the Preface for a good idea of whom this book is for as well as a few alternative references if you need more background information. If you re already comfortable with ActionScript and are reading this text as an introduction to version 3.0 you may want to skim this chapter. In any case .