Beginning
If you want to know something that is rapidly approaching obsolescence, AS2 is what you are looking for. If you want to learn a powerful language with a future and many career opportunities, then AS3 is the way to go.
I highly recommend Colin Moock's Essential Actionscript books for both versions.
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I would definitely go with AS3. AS2 and AS3 are very VERY similar, but there are some significant differences and AS3 has become the standard. If for some reason you need to do a project in AS2 after learning AS3, I don't think you will have a big problem.
ActionScript is very different from Lingo. I don't think there are many similarities other than those that are similar in all scripting languages. However, one of the programmers I work with came from a Lingo background and was very quick to pick up ActionScript.
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I would most definitely recognize AS3 as it is the latest version of ActionScript and has some pretty elegant features.
To confuse you further, I also recommend that you take a look at Flex . This is new technology (ish) from Adobe. Think of this as a more expressive way to write user interfaces in ActionScript.
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AS3 is a fully object oriented strict type language, similar to java, but based on ECMAScript, similar to javascript.
Thus, it will syntactically be similar to other "scripts" and may refer to the same Flash player classes as previous versions of ActionScript, however I would say they are NOT the same. The very core of the language has changed so much that the current versions of the flash player have two engines for AS3 and one for older versions.
This suggests that you can learn whatever you want and both versions will be fun in a flash player, but I would go with AS3 as it is a full fledged language and is the future of the flash development platform.
These articles are dated, but they give a clear look at the syntactic differences in AS2 languages.
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Definitely learn ActionScript 3.0. It's more like many other languages (in my opinion) and much more powerful. Admittedly, I really liked AS2 because it was very flexible and allowed you to get away with terrible code methods, but this is why AS3 is the best choice; it makes you become a good programmer.
If you are interested in making games and applets, I recommend Foundation ActionScript 3.0 Animation . It has been on my side since AS3 came out
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Like everyone else, I would go with AS3. It was the first object-oriented language I learned, and I found that learning it really helped me understand concepts in many other languages that I have learned since then.
The book I'd recommend is Teaching ActionScript 3.0 by Rick Schupe and Zevan Rosser. It's very simple and covers all the basics you need to get started. Plus I found it much easier to read than other books I've looked at. Another book that I found very funny and I'll try Learning Actionscript 3.0 is ActionScript 3: Doing Things by Keith Peters. There are just a lot of really cool, simple examples of physics, etc.
I've worked as an AS developer for several years and these two books are the ones that really got me started.
edit: Also, if you are planning on making games in AS3, I found a lot of helpful tutorials on this blog. http://www.emanueleferonato.com/
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