ActionScript: Difference between revisions

| developer = [[Macromedia]] (now dissolved into [[Adobe Inc.|Adobe Systems]])

| influenced_by = [[HyperTalk]], [[JavaScript]], [[Java (programming language)|Java]]

'''ActionScript''' is an [[object-oriented programming]] language originally developed by [[Macromedia|Macromedia Inc.]] (later acquired by [[Adobe SystemsInc.|Adobe]]). It is influenced by [[HyperTalk]], the scripting language for [[HyperCard]].<ref>{{cite web|url=http://www.zdnet.com/blog/government/apples-lost-decade-hypercard-and-what-might-not-have-been-if-apple-then-was-like-apple-is-today/10185|archive-url=https://web.archive.org/web/20110421072519/http://www.zdnet.com/blog/government/apples-lost-decade-hypercard-and-what-might-not-have-been-if-apple-then-was-like-apple-is-today/10185|url-status=dead|archive-date=April 21, 2011|title=Apple's lost decade, HyperCard, and what might NOT have been if Apple then was like Apple is today|work=zdnet.com[[ZDNet]]|date=2011-04-17|access-date=2014-12-04}}</ref> It is now an implementation of [[ECMAScript]] (meaning it is a superset of the syntax and semantics of the language more widely known as [[JavaScript]]), though it originally arose as a sibling, both being influenced by [[HyperTalk]]. ActionScript code is usually converted to byte-code format by thea [[compiler]].

ActionScript was initially designed for controlling simple two-dimensional vector animations made in Adobe Flash (formerly Macromedia Flash). Initially focused on animation, early versions of Flash content offered few interactivity features, thus had very limited scripting capabilityability. Later versions added functionality allowing for the creation of web-based games and [[rich web application]]s with streaming media (such as video and audio). Today, ActionScript is suitable for desktop and mobile development through Adobe AIR; it is used in some database applications and in basic robotics as in [[Make Controller Kit]].

Since the arrival of the Flash Player 9 alpha (in 2006), a newer version of ActionScript has been released, ActionScript 3.0. This version of the language is intended to be compiled and run on a version of the [[ActionScriptTamarin Virtual Machine(software)|Tamarin]] thatvirtual hasmachine, beenformerly itselfActionScript completelyVirtual rewrittenMachine from2, thethat groundwas upalso fully rewritten (dubbed AVM2).<ref>{{cite web|url=https://www.adobe.com/devnet/actionscript/articles/six_reasons_as3.html |last1=Brimelow |first1=Lee |title=Six reasons to use ActionScript 3.0 |publisher=Adobe Systems Incorporated |date=August 18, 2008|access-date=June 18, 2010}}</ref> Because of this, code written in ActionScript 3.0 is generally targeted for Flash Player 9 and higher, and will not work in previousprior versions. At the same time, ActionScript 3.0 executes up to 10 times faster than legacy ActionScript code due to the [[Just-in-time compilation|just-in-time compiler]] enhancements.<ref>{{cite web|url=https://www.adobe.com/devnet/actionscript/articles/actionscript3_overview.html |last1=Grossman |first1=Gary |last2=Huang |first2=Emmy |title=ActionScript 3.0 overview |publisher=Adobe Systems Incorporated |date=June 27, 2006|access-date=June 18, 2010}}</ref>

Flash libraries can be used with the XML capabilitiesabilities of the browser to render rich content in the browser. This technology is known as Asynchronous Flash and XML, much like AJAX. Adobe offers its Flex product line to meet the demand for rich web applications built on the Flash runtime, with behaviors and programming done in ActionScript. ActionScript 3.0 forms the foundation of the Flex 2 application programming interface ([[API]]).

* '''Flash Player 6''' added an event-handling model, accessibility controls, and support for [[switch statement|switch]]. The first version with support for the [[Action Message Format|AMF]] (AMF) and [[Real -Time Messaging Protocol|RTMP]] protocols(RTMP) allowed for on demand audio/video streaming.

* '''Flash Player 7''': Additions to it include Cascading Style Sheets ([[CSS]]) styling for text and support for ActionScript 2.0, a programming language based on the ECMAScript 4 Netscape Proposal.<ref>{{cite web|url=http://www.mozilla.org/js/language/es4.html |archive-url=https://web.archive.org/web/20070711065258/http://www.mozilla.org/js/language/es4.html |url-status=dead |archive-date=July 11, 2007 |title=ECMAScript 4 Netscape Proposal |publisher=[[Netscape]] |editor=Waldemar Horwat |date=June 30, 2003 |access-date=April 11, 2019 }}</ref> with [[classClass (computer scienceprogramming)|class]]-based [[inheritanceInheritance (computerobject-oriented scienceprogramming)|inheritance]]. However, ActionScript 2.0 can [[cross compile]] to ActionScript 1.0 [[byte-codebytecode]], so that it can run in Flash Player 6.

* '''Flash Player 9 (initially called 8.5)''' added ActionScript 3.0 with the advent of a new virtual machine, called [[ActionScript Virtual Machine 2]] (AVM2), which coexists with the previous AVM1 needed to support legacy content. Performance increases were a major objective for this release of the player, including a new [[Just In Time-in-time compilation|JITjust-in-time]] (JIT) compiler. Support for binary sockets, [[E4XECMAScript for XML]] (E4X) XML parsing, full-screen mode, and regular expressions were added. This is the first release of the player to be titled Adobe Flash Player.<ref>{{cite web|url=https://www.adobe.com/products/flashplayer |title=Flash Player &#124; Adobe Flash Player 11 &#124; Overview |publisher=Adobe.com |date=April 9, 2013 |access-date=April 22, 2013}}</ref>

* '''Flash Player 10 (initially called Astro)''': Added basic [[3D computer graphics|3D]] manipulation, such as rotating on the X, Y, and Z axis, a 3D drawing API, and [[texture mapping]]. Ability to create custom filters using [[Adobe Pixel Bender]]. Several visual processing tasks are now offloaded to the [[GPU]] which gives a noticeable decrease to rendering time for each frame, resulting in higher [[frame rate]]s, especially with [[H.264]] video. There is a new sound API which allows for custom creation of audio in flash, something that has never been possible before.<ref>{{cite web|url=http://labs.adobe.com/technologies/flashplayer10/ |title=Adobe Labs – Adobe Flash Player 10.1 |publisher=Labs.adobe.com |access-date=December 17, 2009| archive-url= https://web.archive.org/web/20100105125609/http://labs.adobe.com/technologies/flashplayer10/| archive-date= January 5, 2010 | url-status= live}}</ref> Furthermore, Flash Player 10 supports Peer to Peer (P2P) communication with [[Real Time Media Flow Protocol]] (RTMFP).

* '''Flash Player 11''': The major addition in this version are the [[Stage3D]]-based advanced (graphic card accelerated) 3D capabilities for Windows Desktop, Mac Desktop, [[iOS]], [[Android (operating system)|Android]], and other major platforms. Significant compatibility improvements have been added for the iOS platform, and other non-desktop platforms. Other features include H.264 encoding for cameras, Native [[JSON]] support, Cubic Bézier Curves, a secure random number generator, [[LZMA]] compression for swfSWF files, workers to offload some code execution to other processor threads, graphics card accelerated camera feed rendering, memory intrinsics and performance analysis, and the ActionScript Compiler 2.0, as well as some other minor additions.<ref>{{cite web|url=http://download.macromedia.com/pub/labs/flashplatformruntimes/shared/flashplayer11_air3_b1_releasenotes_071311.pdf |archive-url=https://web.archive.org/web/20110714222550/http://download.macromedia.com/pub/labs/flashplatformruntimes/shared/flashplayer11_air3_b1_releasenotes_071311.pdf |url-status=dead |archive-date=2011-07-14 |title=Flash Player 11 and AIR 3 Release Notes for Adobe Labs }}</ref>

* '''Flash Player 11.6''': Released in March 2013, it focuses on performance improvements, security enhancements, and stability. Some of the features in this release include ability to query graphics vector data at runtime, full-screen permission dialog user interface improvements, ability to load SWFs at runtime when deploying as an AIR application in AOT mode on iOS, finer-grained control over supported display resolution on iOS devices when deploying as an AIR application, HiDPI support for Flash Professional, and ActionScript 3 access to fast memory operations/intrinsics.

* '''Flash Player 11.7''': Released in June 2013, code-named "Geary", this release focuses on premium video, gaming, security, and stability. Some of the features planned for this release include Android captive runtime debugging, support for the [[Ouya|OUYA]] controller, remote hosting of SWF files on iOS, and preventing backup of shared objects on iOS for better iCloud support.

* '''Flash Player 11.8''': Adobe was planning to release this version in the early part of the second half of 2013, code-named "Harrison". This release focused on premium video, gaming, security, and stability. Some of the features in this release would have included recursive stop API on MovieClips and GamePad support on desktop browsers and Android.

With the release of Flash 5 in September 2000, the "actions" from Flash 4 were enhanced once more and named "ActionScript" for the first time.<ref>{{Cite web|url=https://helpx.adobe.com/x-productkb/multi/release-notes-flash-player-11.html|title=Flash Player 11, AIR 3 Release Notes|website=helpx.adobe.com|access-date=2016-10-07}}</ref> This was the first version of ActionScript with influences from [[JavaScript]] and the [[ECMA-262]] (Third Edition) standard, supporting the said standard's object model and many of its core [[data type]]s. Local variables may be declared with the {{Mono|var}} statement, and user-defined [[function (computer science)|functions]] with [[parameter (computer science)|parameter]] passing and [[return statement|return]] values can also be created. Notably, ActionScript could now also be typed with a text editor rather than being assembled by choosing actions from drop-down lists and dialog box controls. With the next release of its authoring tool, Flash MX, and its corresponding player, [[Adobe Flash Player|Flash Player 6]], the language remained essentially unchanged; there were only minor changes, such as the addition of the {{Mono|switch}} statement and the "strict equality" ({{Mono|1====}}) operator, which brought it closer to being [[ECMA-262]]-compliant. Two important features of ActionScript that distinguish it from later versions are its loose type system and its reliance on prototype-based [[inheritance (computerobject-oriented scienceprogramming)|inheritance]]. Loose typing refers to the ability of a [[variable (programming)|variable]] to hold any type of data. This allows for rapid script development and is particularly well-suited for small-scale scripting projects. Prototype-based inheritance is the ActionScript 1.0 mechanism for code reuse and object-oriented programming. Instead of a {{Mono|class}} keyword that defines common characteristics of a [[class (computer science)|class]], ActionScript 1.0 uses a special object that serves as a "prototype" for a class of objects. All common characteristics of a class are defined in the class's prototype object and every [[Instantiation (computer science)|instance]] of that class contains a link to that prototype object.

The next major revision of the language, ActionScript 2.0, was introduced in September 2003 with the release of Flash MX 2004 and its corresponding player, [[Adobe Flash Player|Flash Player 7]]. In response to user demand for a language better equipped for larger and more complex applications, ActionScript 2.0 featured compile-time [[type checking]] and class-based [[syntax of programming languages|syntax]], such as the keywords {{Mono|class}} and {{Mono|extends}}. While this allowed for a more structured object-oriented programming approach, the code would still be compiled to ActionScript 1.0 [[bytecode]], allowing it to be used on the preceding Flash Player 6 as well. In other words, the [[Class-based programming|class-based]] inheritance syntax was a layer on top of the existing prototype-based system. With ActionScript 2.0, developers could constrain [[variable (programming)|variables]] to a specific type by adding a type annotation so that type mismatch errors could be found at [[compile-time]]. ActionScript 2.0 also introduced class-based inheritance syntax so that developers could create classes and interfaces, much as they would in class-based languages such as [[Java (programming language)|Java]] and [[C++]]. This version conformed partially to the [[ECMAScript]] Fourth Edition draft specification.

* '''[[Flash Lite]] 1.0''': Flash Lite is the Flash technology specifically developed for mobile phones and consumer electronics devices. Supports Flash 4 ActionScript.

* '''Object''' – Object is the data type all complex data types inherit from. It allows for the grouping of methods, functions, parameters, and other objects.

* '''TextField''' + A simple dynamic or input text field. Inherits the MovieclipMovieClip type.

* '''void''' – The data type contains only one value, undefined. In previous versions of ActionScript, undefined was the default value for instances of the Object class. In ActionScript 3.0, the default value for Object instances is booleanBoolean.

* '''Array''' + Contains a list of data. Though ActionScript 3 is a strongly typed language, the contents of an Array may be of any type and values must be cast back to their original type after retrieval. (Supportsupport for typed Arrays has recently been added with the Vector class.).

* '''Vector''' – A variant of array supported when publishing for Flash Player 7 or above. Vectors are typed, dense Arrays (values must be defined or booleanBoolean) which may be fixed-length, and are bounds-checked during retrieval. Vectors are not just more typesafe than Arrays but also perform faster.

Only references to an object may be removed by using the "delete" keyword. Removal of actual objects and data is done by the Flash Player garbage collector which checks for any existing references in the Flash memory space. If none are found (no other reference is made to the orphaned object), it is removed from memory. For this reason, memory management in ActionScript requires careful application development planning.

* [http://help.adobe.com/en_US/AS2LCR/Flash_10.0/help.html?content=Part2_AS2_LangRef_1.html ActionScript 2.0 Language Reference] {{Webarchive|url=https://web.archive.org/web/20130131044759/http://help.adobe.com/en_US/AS2LCR/Flash_10.0/help.html?content=Part2_AS2_LangRef_1.html |date=January 31, 2013 }}