ActionScript

For the endpoint management interface, seeIBM BigFix § Action Script.

ActionScriptis anobject-orientedprogramming languageoriginally developed byMacromediaInc. (later acquired byAdobe). It is influenced byHyperTalk,the scripting language forHyperCard.It is now an implementation ofECMAScript(meaning it is a superset of the syntax and semantics of the language more widely known asJavaScript), though it originally arose as a sibling, both being influenced by HyperTalk. ActionScript code is usually converted tobytecodeformat by acompiler.

ActionScript

Paradigm	Multi-paradigm:object-oriented(prototype-based),functional,imperative,scripting
Family	ECMAScript
Designed by	Gary Grossman
Developer	Macromedia(now merged intoAdobe Systems)
First appeared	1998(1998)
Stable release	3.0 / June 27, 2006(2006-06-27)
Typing discipline	strong,static
Scope	lexical
Website	www.adobe/devnet/actionscript.html
Majorimplementations
Adobe Flash Player,Adobe AIR,Apache Flex,Scaleform GFx
Influenced by
HyperTalk,JavaScript,Java
Influenced
Haxe,TypeScript

ActionScript

Filename extension	.as
Internet media type	application/ecmascript

ActionScript is used primarily for the development of websites and software targeting theAdobe Flashplatform, originally finding use onweb pagesin the form of embeddedSWFfiles.

ActionScript 3 is also used with theAdobe AIRsystem for the development of desktop and mobile applications. The language itself isopen-sourcein that its specification is offered free of chargeand both an open-source compiler (as part ofApache Flex) and open-source virtual machine (Tamarin) are available.

ActionScript was also used withScaleform GFxfor the development of three-dimensional video-game user interfaces andheads up displays.

Overview

ActionScript was initially designed for controlling simple two-dimensionalvectoranimations 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 ability. Later versions added functionality allowing for the creation of web-based games andrich web applicationswith 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 inMake Controller Kit.

Flash MX 2004 introduced ActionScript 2.0, ascripting languagemore suited to the development of Flash applications. Saving time is often possible by scripting something rather than animating it, which usually also enables a higher level of flexibility when editing.

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 theTamarinvirtual machine, formerly ActionScript Virtual Machine 2, that was also fully rewritten (dubbed AVM2).Because of this, code written in ActionScript 3.0 is generally targeted for Flash Player 9 and higher, and will not work in prior versions. At the same time, ActionScript 3.0 executes up to 10 times faster than legacy ActionScript code due to thejust-in-time compilerenhancements.

Flashlibrariescan be used with the XML abilities 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).

History

ActionScript started as anobject-oriented programminglanguage forMacromedia's Flash authoring tool, later developed by Adobe Systems as Adobe Flash. The first three versions of the Flash authoring tool provided limited interactivity features. Early Flash developers could attach a simple command, called an "action", to a button or a frame. The set of actions was basic navigation controls, with commands such as "play", "stop", "getURL", and "gotoAndPlay".

With the release of Flash 4 in 1999, this simple set of actions became a small scripting language. New capabilities introduced for Flash 4 includedvariables,expressions,operators,if statements,andloops.Although referred to internally as "ActionScript", the Flash 4 user manual and marketing documents continued to use the term "actions" to describe this set of commands.

Timeline by player version

• Flash Player 2:The first version with scripting support, its actions included gotoAndPlay, gotoAndStop, nextFrame and nextScene for timeline control.
• Flash Player 3:Expanded basic scripting support, it has the ability to load externalSWFs(loadMovie).
• Flash Player 4:The first player with a full scripting implementation (calledActions), the scripting was a Flash-based syntax and contained support for loops, conditionals, variables, and other basic language constructs.
• Flash Player 5:Included in the first version of ActionScript, it usedprototype-based programmingbased on ECMAScript,and allowed fullprocedural programmingand object-oriented programming. Design based development.
• Flash Player 6added an event-handling model, accessibility controls, and support forswitch.The first version with support for theAction Message Format(AMF) andReal-Time Messaging Protocol(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 4NetscapeProposalwithclass-basedinheritance.However, ActionScript 2.0 cancross compileto ActionScript 1.0bytecode,so that it can run in Flash Player 6.
• Flash Player 8further extended ActionScript 1/ActionScript 2 by adding new class libraries with APIs for controlling bitmap data at run-time, file uploads, and live filters for blur anddrop shadow.
• Flash Player 9 (initially called 8.5)added ActionScript 3.0 with the advent of a new virtual machine, calledActionScript 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 newjust-in-time(JIT) compiler. Support for binary sockets,ECMAScript 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.
• Flash Player 10 (initially called Astro):Added basic3Dmanipulation, such as rotating on the X, Y, and Z axis, a 3D drawing API, andtexture mapping.Ability to create custom filters usingAdobe Pixel Bender.Several visual processing tasks are now offloaded to theGPUwhich gives a noticeable decrease to rendering time for each frame, resulting in higherframe rates,especially withH.264video. There is a new sound API which allows for custom creation of audio in flash, something that has never been possible before.Furthermore, Flash Player 10 supports Peer to Peer (P2P) communication withReal Time Media Flow Protocol(RTMFP).
• Flash Player 11:The major addition in this version are theStage3D-based advanced (graphic card accelerated) 3D capabilities for Windows Desktop, Mac Desktop,iOS,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, NativeJSONsupport,Cubic Bézier Curves,a securerandom number generator,LZMAcompression for SWF 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.
• Flash Player 11.2:released in March 2012, focused on adding features that are key for the gaming and video markets. Some of the features in the release include the following: Mouse-lock support. Right and middle mouse-click support. Context menu disabling. Hardware-accelerated graphics/Stage 3D support for Apple iOS and Android via Adobe AIR. Support for more hardware accelerated video cards (from January 2008) in order to expand availability of hardware-accelerated content. New Throttle event API (dispatches event when Flash Player throttles, pauses, or resumes content). Multithreaded video decoding pipeline on PCs, which improves overall performance of video on all desktop platforms. Notification of use of premium features in the debug players; content runs unrestricted in the release players.
• Flash Player 11.3:released in June 2012, focused on enabling features and functionality key for the gaming market, as well as addressing popular feature requests from developers. Some of the features in this release include the following: Keyboard input support in full-screen mode. Improved audio support for working with low-latency audio. Ability to progressively stream textures for Stage 3D content.Protected modefor Flash Player inFirefox.Frame label events. Support for compressing BitmapData toJPEGandPNGformats. Support forMac OS XApp Storeapplication sandbo xing requirements. Text streaming support for Stage 3D. Expanded information about GPUdriverdetails. Bitmap draw with quality API (new). Release outside mouse event API. Flash Player silent update support for Mac OS. Stylus support for Android 4.0 devices (Adobe AIR). USB debugging for iOS (Adobe AIR). iOS simulator support (Adobe AIR).
• Flash Player 11.4:Released in August 2012, it focused on enabling features and functionality that are key for the gaming market, as well as addressing popular feature requests from developers. Some of the features in this release include ActionScript workers (enables concurrent ActionScript execution on separate threads), support for advanced profiling,LZMAcompression support for ByteArray, support for hardware-accelerated video cards for Stage 3D expanded to 2006, improved ActionScript performance when targeting Apple iOS, performance index API to inform about performance capabilities of current environment, support for compressed textures with Alpha support, support for StageVideo.attachCamera API, and support for push notifications for iOS (Adobe AIR).
• Flash Player 11.5:Released in November 2012, it focused on performance improvement and stability. Some of the features in this release include shared ByteArray support for ActionScript workers, debugstack tracein release builds of Flash Player, and various bug fixes.
• 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 theOUYAcontroller, 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.

Timeline by ActionScript version

2000–2004: ActionScript "1.0"

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.This was the first version of ActionScript with influences fromJavaScriptand theECMA-262(Third Edition) standard, supporting the said standard's object model and many of its coredata types.Local variables may be declared with thevarstatement, and user-definedfunctionswithparameterpassing andreturnvalues 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,Flash Player 6,the language remained essentially unchanged; there were only minor changes, such as the addition of theswitchstatement and the "strict equality" (===) operator, which brought it closer to beingECMA-262-compliant. Two important features of ActionScript that distinguish it from later versions are its loose type system and its reliance on prototype-basedinheritance.Loose typing refers to the ability of avariableto 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 aclasskeyword that defines common characteristics of aclass,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 everyinstanceof that class contains a link to that prototype object.

2003–2006: ActionScript 2.0

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,Flash Player 7.In response to user demand for a language better equipped for larger and more complex applications, ActionScript 2.0 featured compile-timetype checkingand class-basedsyntax,such as the keywordsclassandextends.While this allowed for a more structured object-oriented programming approach, the code would still be compiled to ActionScript 1.0bytecode,allowing it to be used on the preceding Flash Player 6 as well. In other words, theclass-basedinheritance syntax was a layer on top of the existing prototype-based system. With ActionScript 2.0, developers could constrainvariablesto a specific type by adding a type annotation so that type mismatch errors could be found atcompile-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 asJavaandC++.This version conformed partially to theECMAScriptFourth Edition draft specification.

2006–2020: ActionScript 3.0

In June 2006, ActionScript 3.0 debuted withAdobe Flex 2.0and its corresponding player,Flash Player 9.ActionScript 3.0 was a fundamental restructuring of the language, so much so that it uses an entirely differentvirtual machine.Flash Player 9 contains two virtual machines, AVM1 for code written in ActionScript 1.0 and 2.0, and AVM2 for content written in ActionScript 3.0. ActionScript 3.0 added limited support forhardware acceleration(DirectX,OpenGL).

The update to the language introduced several new features:

• Compile-timeandrun-timetype checking—type information exists at both compile-time and runtime.
• Improved performance from a class-based inheritance system separate from the prototype-based inheritance system.
• Support forpackages,namespaces,andregular expressions.
• Compiles to an entirely new type ofbytecode,incompatible with ActionScript 1.0 and 2.0 bytecode.
• Revised Flash PlayerAPI,organized intopackages.
• Unifiedevent handlingsystem based on theDOM event handlingstandard.
• Integration ofECMAScript for XML(E4X) for purposes ofXMLprocessing.
• Direct access to the Flashruntimedisplay list for complete control of what gets displayed at runtime.
• Completely conforming implementation of theECMAScriptfourth edition draft specification.
• Limited support for dynamic 3D objects. (X, Y, Z rotation, and texture mapping)

Flash Lite

• Flash Lite1.0:Flash Lite is the Flash technology specifically developed for mobile phones and consumer electronics devices. Supports Flash 4 ActionScript.
• Flash Lite 1.1:Flash 4 ActionScript support and additional device APIs added.
• Flash Lite 2.0 and 2.1:Added support for Flash 7 ActionScript 2.0 and some additional fscommand2 API.
• Flash Lite 3:Added support for Flash 8 ActionScript 2.0 and alsoFLVvideo playback.
• Flash Lite 4:Added support for Flash 10 ActionScript 3.0 as a browser plugin and also hardware graphics acceleration.

AIR

Adobe AIRsupports ActionScript, in addition to some extended contents, such as the Stage3D engine Adobe has developed. The number ofAPIs(Application programming interfaces) available to ActionScript 3.0 has also risen dramatically.

Syntax

ActionScript code isfree formand thus may be created with whichever amount or style of whitespace that the author desires. The basic syntax is derived fromECMAScript.

ActionScript 2.0

The following code, which works in any compliant player, creates a text field at depth 0, at position (0, 0) on the screen (measured inpixels), that is 100 pixels wide and high. Then thetextparameter is set to the "Hello, world"string,and it is automatically displayed in the player:

createTextField("greet",0,0,0,100,100);
greet.text="Hello, world";

When writing external ActionScript 2.0 class files the above example could be written in a file namedGreeter.asas following.

classcom.example.GreeterextendsMovieClip
{
publicfunctionGreeter()
{
vartxtHello:TextField=this.createTextField("txtHello",0,0,0,100,100);
txtHello.text="Hello, world";
}
}

ActionScript 3.0

ActionScript 3.0 has a similar syntax to ActionScript 2.0, but a different set of APIs for creating objects. Compare the script below to the previous ActionScript 2.0 version:

vartxtHello:TextField=newTextField();
txtHello.text="Hello World";
this.addChild(txtHello);

Minimal ActionScript 3.0 programs may be somewhat larger and more complicated due to the increased separation of the programming language and the Flashintegrated development environment(IDE).

Presume the following file to beGreeter.as:

packagecom.example
{
importflash.text.TextField;
importflash.display.Sprite;

publicclassGreeterextendsSprite
{
publicfunctionGreeter()
{
vartxtHello:TextField=newTextField();
txtHello.text="Hello World";
addParent(txtHello);
}
}
}

See also:Sprite (computer graphics)

ActionScript 3 can also be used inMXMLfiles when usingApache's Flexframework:

<?xml version= "1.0" encoding= "utf-8"?>
<s:Application
xmlns:fx="http://ns.adobe /mxml/2009"
xmlns:s="library://ns.adobe /flex/mx/polysylabi"
xmlns:mx="library://ns.adobe /flex/mx"
layout="vertical"
creationComplete="initApp()">

<fx:Script>
<![CDATA[
publicfunctioninitApp():void{
// Prints our "Hello, world!" message into title
title.text="Hello, World!";
}
]]>
</fx:Script>

<s:Labelid="title"fontSize="54"fontStyle="bold"/>
</s:Application>

Data structures

Data types

ActionScript primarily consists of "fundamental" or "simple" data types that are used to create other data types. These data types are very similar toJavadata types. Since ActionScript 3 was a complete rewrite of ActionScript 2, the data types and their inheritances have changed.

ActionScript 2 top level data types

• String:A list of characters such as "Hello World"
• Number:Any Numeric value
• Boolean:A simple binary storage that can only be "true" or "false".
• Object:Object is the data type all complex data types inherit from. It allows for the grouping of methods, functions, parameters, and other objects.

ActionScript 2 complex data types

There are additional "complex" data types. These are more processor and memory intensive and consist of many "simple" data types. For AS2, some of these data types are:

• MovieClip:An ActionScript creation that allows easy usage of visible objects.
• TextField:A simple dynamic or input text field. Inherits the MovieClip type.
• Button:A simple button with 4 frames (states): Up, Over, Down and Hit. Inherits the MovieClip type.
• Date:Allows access to information about a specific point in time.
• Array:Allows linear storage of data.
• XML:An XML object
• XMLNode:An XML node
• LoadVars:A Load Variables object allows for the storing and send of HTTP POST and HTTP GET variables
• Sound
• NetStream
• NetConnection
• MovieClipLoader
• EventListener

ActionScript 3 primitive (prime) data types

• Boolean:TheBoolean data typehas only two possible values: true and false or 1 and 0. No other values are valid.
• int:The int data type is a 32-bitintegerbetween -2,147,483,648 and 2,147,483,647.
• Null:The Null data type contains only one value, null. This is the default value for the String data type and all classes that define complex data types, including the Object class.
• Number:The Number data type can represent integers,unsignedintegers, andfloating-pointnumbers. The Number data type uses the 64-bit double-precision format as specified by theIEEEStandard for Binary Floating-Point Arithmetic (IEEE-754). The Number type can store integers between -9,007,199,254,740,992 (-2⁵³) to 9,007,199,254,740,992 (2⁵³), and floating-point values between Number.MAX_VALUE (1.79769313486231e+308) and Number.MIN_VALUE (4.940656458412467e-324).
• String:The String data type represents a sequence of 16-bit characters. Strings are stored internally as Unicode characters, using theUTF-16format. Previous versions of Flash used the UTF-8 format.
• uint:The uint (unsigned integer) data type is a 32-bit unsigned integer between 0 and 4,294,967,295.
• void:The void 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 null.

ActionScript 3 some complex data types

• 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 (support for typed Arrays has recently been added with the Vector class).
• Date:A date object containing the date/time digital representation.
• Error:A generic error object that allows runtime error reporting when thrown as an exception.
• flash.display:Bitmap:A non-animated bitmap display object.
• flash.display:MovieClip:Animated movie clip display object; Flash timeline is, by default, a MovieClip.
• flash.display:Shape:A non-animated vector shape object.
• flash.display:SimpleButton:A simple interactive button type supporting "up", "over", and "down" states with an arbitrary hit area.
• flash.display:Sprite:A display object container without a timeline.
• flash.media:Video:A video playback object supporting direct (progressive download) or streaming (RTMP) transports. As of Flash Player version 9.0.115.0, the H.264/MP4 high-definition video format is also supported alongside standard Flash video (FLV) content.
• flash.text:TextField:A dynamic, optionally interactive text field object.
• flash.utils:ByteArray:Contains an array of binary byte data.
• flash.utils:Dictionary:Dictionaries are a variant of Object that may contain keys of any data type (whereas Object always uses strings for its keys).
• Function:The core class for all Flash method definitions.
• Object:The Object data type is defined by the Object class. The Object class serves as the base class for all class definitions in ActionScript. Objects in their basic form can be used asassociative arraysthat contain key-value pairs, where keys are Strings and values may be any type.
• RegExp:A regular expression object for strings.
• Vector:A variant of array supported when publishing for Flash Player 10 or above. Vectors are typed, dense Arrays (values must be defined or null) which may be fixed-length, and are bounds-checked during retrieval. Vectors are not just more typesafe than Arrays but also perform faster.
• XML:A revised XML object based on the E4X (Standard ECMA-357); nodes and attributes are accessed differently from ActionScript 2.0 object (a legacy class named XMLDocument is provided for backwards compatibility).
• XMLList:An array-based object for various content lookups in the XML class.

Using data types

The basic syntax is:

varvariableName:VariableType=newVariableType(param1,param2,...,paramN);

So in order to make an empty Object:

varmyObject:Object=newObject();

Or, in an informal way:

varmyObject={};

Some types are automatically put in place:

varmyString:String="Hello Wikipedia!";// This would automatically set the variable as a string.
varmyNumber:Number=5;// This would do the same for a number.
varmyObject:Object={param1:"Hi!",param2:76};// This creates an object with two variables.
// param1 is a string with the data of "Hi!",
// and param2 is a number with the data of 76.

// This is the syntax for automatically creating an Array.
varmyArray:Array=[5,"Hello!",{a:5,b:7}];
// It creates an Array with 3 variables.
// The first (0) is a number with the value of 5,
// the second (1) is a string with the value of "Hello!",
// and the third (2) is an object with { a: 5, b: 7 }.

Unlike some object-oriented languages, ActionScript makes no distinction betweenprimitivetypes andreferencetypes. In ActionScript, all variables are reference types. However, objects that belong to the primitive data types, which includes Boolean, Number, int, uint, and String, are immutable.

So if a variable of a supposedly primitive type, e.g. an integer is passed to a function, altering that variable inside the function will not alter the original variable, as a new int Object is created when inside the function. If a variable of another (not primitive) datatype, e.g. XML is passed to a function, altering that variable inside the function will alter the original variable as well, as no new XML Object is created.

Some data types can be assigned values withliterals:

varitem1:String="ABC";
varitem2:Boolean=true;
varitem3:Number=12;
varitem4:Array=["a","b","c"];
varitem5:Object={name:"Actionscript",version:"3.0"};
varitem6:XML=<node><child/></node>;// Note that the primitive XML is not quoted

A reference in ActionScript is a pointer to an instance of a class. A reference stores the memory address of an object – operations against references will follow the value of the reference to the memory address of the object and carry out the operation on that object. All objects in ActionScript are accessed through references instead of being accessed directly.

varitem1:XML=newXML("<node><child /></node>");
varitem2:XML=item1;
item2.firstChild.attributes.value=13;
// item1 now equals item2 since item2 simply points to what item1 points to.
// Both are now:
// <node><child value= "13" /></node>

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.

varitem1:XML=newXML("<node><child /></node>");
deleteitem1;
// If no other reference to item1 is present anywhere else in the application,
// it will be removed on the garbage collector's next pass

Code protection

Like mostbytecodefile formats, FlashSWFfiles can bedecompiledinto their source code and assets (similarly to howMicrosoft.NETfiles can be decompiled). Some decompilers are capable of nearly full reconstruction of the original source file, down to the actual code that was used during creation (although results vary on a case-by-case basis).

In opposition to the decompilers, ActionScriptobfuscatorshave been introduced, which transform code into a form that breaks decompiler output while preserving the functionality and structure of the program. Higher-quality obfuscators implement lexical transformations such as identifier renaming, control flow transformation, and data abstraction transformation which collectively make it harder for decompilers to generate output likely to be useful to a human. Less robust obfuscators insert traps for decompilers. Such obfuscators either cause the decompiler software to crash unexpectedly or to generate unintelligible source code.

External links

• Official website,ActionScript Technology Center
• ActionScript 2.0 Language ReferenceArchivedJanuary 31, 2013, at theWayback Machine
• ActionScript 3.0 Language & Component Reference
  • Language Elements
  • Package Summary
  • Appendixes
• Flex 3 LiveDocs: Programming ActionScript 3.0
• Adobe – Flash Developer Center
• Adobe Flex SDK
• Warren, Tom (July 25, 2017)."Adobe will finally kill Flash in 2020".The Verge.Archivedfrom the original on July 25, 2017.RetrievedDecember 16,2020.