Object-oriented programming is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction,...
Macromedia was an American graphics and web development software company headquartered in San Francisco, California that produced such products as Flash and Dreamweaver. Its rival, Adobe Systems, acquired Macromedia on December 3, 2005 and controls the line of Macromedia...
ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known dialects such as JavaScript, JScript, and ActionScript.- History :JavaScript...
(meaning it is a superset of the syntax and semantics of the language more widely known JavaScript
JavaScript
JavaScript is a prototype-based scripting language that is dynamic, weakly typed and has first-class functions. It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles....
), and is used primarily for the development of websites and software targeting the Adobe Flash Player
Adobe Flash Player
The Adobe Flash Player is software for viewing multimedia, Rich Internet Applications and streaming video and audio, on a computer web browser or on supported mobile devices. Flash Player runs SWF files that can be created by the Adobe Flash authoring tool, by Adobe Flex or by a number of other...
A web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext...
s in the form of embedded SWF files. The language itself is open-source in that its specification is offered free of charge and both an open source compiler (as part of Adobe Flex
Adobe Flex
Adobe Flex is a software development kit released by Adobe Systems for the development and deployment of cross-platform rich Internet applications based on the Adobe Flash platform...
Tamarin is a free virtual machine with just-in-time compilation support intended to implement the fourth edition of the ECMAScript standard....
) are available.
ActionScript was initially designed for controlling simple 2D vector animations made in Adobe Flash
Adobe Flash
Adobe Flash is a multimedia platform used to add animation, video, and interactivity to web pages. Flash is frequently used for advertisements, games and flash animations for broadcast...
(formerly Macromedia Flash). Initially focused on animation, early versions of Flash content offered few interactivity features and thus had very limited scripting capability. Later versions added functionality allowing for the creation of Web-based games and rich Internet application
Rich Internet application
A Rich Internet Application is a Web application that has many of the characteristics of desktop application software, typically delivered either by way of a site-specific browser, via a browser plug-in, independent sandboxes, extensive use of JavaScript, or virtual machines...
s with streaming media (such as video and audio). Today, ActionScript is suitable for use in some database applications, and in basic robotics, as with the Make Controller Kit.
Flash MX 2004 introduced ActionScript 2.0, a scripting programming language more suited to the development of Flash applications. It is often possible to save time 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. ActionScript 3.0 is an object-oriented programming language
Object-oriented programming language
This is a list of object-oriented programming programming languages.-Languages with object-oriented features:*ABAP*Ada 95*AmigaE*BETA*Blue*Boo*C++*C#*COBOL*Cobra*ColdFusion*Common Lisp*COOL*CorbaScript*Clarion*CLU*Curl*D*Dylan*E*Eiffel...
allowing far more control and code reusability when building complex Flash applications. This version of the language is intended to be compiled and run on a version of the ActionScript Virtual Machine that has been itself completely re-written from the ground up (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 previous versions. At the same time, ActionScript 3.0 executes up to 10 times faster than legacy ActionScript code.
Flash libraries can be used with the XML capabilities of the browser to render rich content in the browser. This technology is known as Asynchronous Flash and XML, much like AJAX
Ajax (programming)
Ajax is a group of interrelated web development methods used on the client-side to create asynchronous web applications...
Adobe Flex is a software development kit released by Adobe Systems for the development and deployment of cross-platform rich Internet applications based on the Adobe Flash platform...
product line to meet the demand for Rich Internet Applications built on the Flash runtime, with behaviors and programming done in ActionScript. ActionScript 3.0 forms the foundation of the Flex 2 API.
History
Action Script started as an Object-oriented language for Macromedia
Macromedia
Macromedia was an American graphics and web development software company headquartered in San Francisco, California that produced such products as Flash and Dreamweaver. Its rival, Adobe Systems, acquired Macromedia on December 3, 2005 and controls the line of Macromedia...
's Flash authoring tool, now developed by Adobe Systems
Adobe Systems
Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...
Adobe Flash is a multimedia platform used to add animation, video, and interactivity to web pages. Flash is frequently used for advertisements, games and flash animations for broadcast...
. 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
Scripting language
A scripting language, script language, or extension language is a programming language that allows control of one or more applications. "Scripts" are distinct from the core code of the application, as they are usually written in a different language and are often created or at least modified by the...
. New capabilities introduced for Flash 4 included variables
Variable (programming)
In computer programming, a variable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents...
An expression in a programming language is a combination of explicit values, constants, variables, operators, and functions that are interpreted according to the particular rules of precedence and of association for a particular programming language, which computes and then produces another value...
Programming languages typically support a set of operators: operations which differ from the language's functions in calling syntax and/or argument passing mode. Common examples that differ by syntax are mathematical arithmetic operations, e.g...
, if statements, and loops. 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. Actions included gotoAndPlay, gotoAndStop, nextFrame and nextScene for timeline control.
Flash Player 3: Expanded basic scripting support with the ability to load external SWF
SWF
SWF is an Adobe Flash file format used for multimedia, vector graphics and ActionScript. Originating with FutureWave Software, then transferred to Macromedia, and then coming under the control of Adobe, SWF files can contain animations or applets of varying degrees of interactivity and function.,...
s (loadMovie).
Flash Player 4: First player with a full scripting implementation (called Actions). The scripting was a flash based syntax and contained support for loops, conditionals, variables and other basic language constructs.
Prototype-based programming is a style of object-oriented programming in which classes are not present, and behavior reuse is performed via a process of cloning existing objects that serve as prototypes. This model can also be known as classless, prototype-oriented or instance-based programming...
Procedural programming can sometimes be used as a synonym for imperative programming , but can also refer to a programming paradigm, derived from structured programming, based upon the concept of the procedure call...
Object-oriented programming is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction,...
.
Flash Player 6: Added an event handling model, accessibility controls and support for switch
Switch statement
In computer programming, a switch, case, select or inspect statement is a type of selection control mechanism that exists in most imperative programming languages such as Pascal, Ada, C/C++, C#, Java, and so on. It is also included in several other types of languages...
Action Message Format is a binary format used to serialize objects graphs such ActionScript objects and XML, or send messages between an Adobe Flash client and a remote service, usually a Flash Media Server or third party alternatives....
Real Time Messaging Protocol was initially a proprietary protocol developed by Macromedia for streaming audio, video and data over the Internet, between a Flash player and a server...
protocols which allowed for on demand audio/video streaming.
Flash Player 7: Additions include CSS styling for text and support for ActionScript 2.0, a programming language based on the ECMAScript 4 Netscape Proposal with class
Class (computer science)
In object-oriented programming, a class is a construct that is used as a blueprint to create instances of itself – referred to as class instances, class objects, instance objects or simply objects. A class defines constituent members which enable these class instances to have state and behavior...
In object-oriented programming , inheritance is a way to reuse code of existing objects, establish a subtype from an existing object, or both, depending upon programming language support...
. However, ActionScript 2.0 can cross compile to ActionScript 1.0 byte-code, so that it can run in Flash Player 6.
Flash Player 8: Further 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 and dropshadow.
Flash Player 9 (initially called 8.5): Added ActionScript 3.0 with the advent of a new virtual machine, called AVM2 (ActionScript Virtual Machine 2), 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 JIT compiler. Support for binary sockets, E4X
E4X
ECMAScript for XML is a programming language extension that adds native XML support to ECMAScript . The goal is to provide an alternative to DOM interfaces that uses a simpler syntax for accessing XML documents. It also offers a new way of making XML visible...
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 basic 3D
3D computer graphics
3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...
manipulation, such as rotating on the X, Y, and Z axis, a 3D drawing API, and texture mapping
Texture mapping
Texture mapping is a method for adding detail, surface texture , or color to a computer-generated graphic or 3D model. Its application to 3D graphics was pioneered by Dr Edwin Catmull in his Ph.D. thesis of 1974.-Texture mapping:...
Adobe Pixel Bender, previously codenamed Hydra, is a programming language created by Adobe Systems for the description of image processing algorithms...
. 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
Frame rate
Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
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. Furthermore, Flash Player 10 supports Peer to Peer (P2P) communication with Real Time Media Flow Protocol
Real Time Media Flow Protocol
Real Time Media Flow Protocol is a proprietary protocol developed by Adobe Systems. RTMFPenables low latency UDP streamings and direct peer-to-peer communication between multiple Adobe Flash Players...
(RTMFP).
Flash Player 11: The major addition in this version are advanced (graphics accelerated) 3D capabilities. Other features include H.264 encoding for cameras, Native JSON support, Cubic Bézier Curves, a secure random number generator, LZMA compression for swf files as well as some other minor additions.
Timeline by ActionScript version
2000–2003: 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 from JavaScript
JavaScript
JavaScript is a prototype-based scripting language that is dynamic, weakly typed and has first-class functions. It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles....
and the ECMA-262 (Third Edition) standard, supporting the said standard's object model and many of its core data type
Data type
In computer programming, a data type is a classification identifying one of various types of data, such as floating-point, integer, or Boolean, that determines the possible values for that type; the operations that can be done on values of that type; the meaning of the data; and the way values of...
In computer programming, a variable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents...
may be declared with the var statement, and user-defined functions with parameter
Parameter (computer science)
In computer programming, a parameter is a special kind of variable, used in a subroutine to refer to one of the pieces of data provided as input to the subroutine. These pieces of data are called arguments...
In computer programming, a return statement causes execution to leave the current subroutine and resume at the point in the code immediately after where the subroutine was called, known as its return address. The return address is saved, usually on the process's call stack, as part of the operation...
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, Flash Player 6
Adobe Flash Player
The Adobe Flash Player is software for viewing multimedia, Rich Internet Applications and streaming video and audio, on a computer web browser or on supported mobile devices. Flash Player runs SWF files that can be created by the Adobe Flash authoring tool, by Adobe Flex or by a number of other...
, the language remained essentially unchanged; there were only minor changes, such as the addition of the switch statement and the "strict equality" () 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
Inheritance (computer science)
In object-oriented programming , inheritance is a way to reuse code of existing objects, establish a subtype from an existing object, or both, depending upon programming language support...
. Loose typing refers to the ability of a variable
Variable (programming)
In computer programming, a variable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents...
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
Object-oriented programming
Object-oriented programming is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction,...
. Instead of a class keyword that defines common characteristics of a class
Class (computer science)
In object-oriented programming, a class is a construct that is used as a blueprint to create instances of itself – referred to as class instances, class objects, instance objects or simply objects. A class defines constituent members which enable these class instances to have state and behavior...
, 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 instance of 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
Adobe Flash Player
The Adobe Flash Player is software for viewing multimedia, Rich Internet Applications and streaming video and audio, on a computer web browser or on supported mobile devices. Flash Player runs SWF files that can be created by the Adobe Flash authoring tool, by Adobe Flex or by a number of other...
. 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
Syntax of programming languages
In computer science, the syntax of a programming language is the set of rules that define the combinations of symbols that are considered to be correctly structured programs in that language. The syntax of a language defines its surface form...
, such as the keywords class and extends.
(While this allowed for a more structured object-oriented programming approach, the code would still be compiled to ActionScript 1.0 bytecode
Bytecode
Bytecode, also known as p-code , is a term which has been used to denote various forms of instruction sets designed for efficient execution by a software interpreter as well as being suitable for further compilation into machine code...
, allowing it to be used on the preceding Flash Player 6 as well.
In other words, the class-based
Class-based programming
Class-based programming, or more commonly class-orientation, refers to the style of object-oriented programming in which inheritance is achieved by defining classes of objects, as opposed to the objects themselves .The most popular and developed model of OOP is a class-based model, as opposed to an...
In computer science, the syntax of a programming language is the set of rules that define the combinations of symbols that are considered to be correctly structured programs in that language. The syntax of a language defines its surface form...
was a layer on top of the existing prototype-based system.) With ActionScript 2.0, developers could constrain variables
Variable (programming)
In computer programming, a variable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents...
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
Syntax of programming languages
In computer science, the syntax of a programming language is the set of rules that define the combinations of symbols that are considered to be correctly structured programs in that language. The syntax of a language defines its surface form...
so that developers could create classes and interfaces, much as they would in class-based languages such as Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
. This version conformed partially to the ECMAScript
ECMAScript
ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known dialects such as JavaScript, JScript, and ActionScript.- History :JavaScript...
Fourth Edition draft specification.
2006–today: ActionScript 3.0
In June 2006, ActionScript 3.0 debuted with Adobe Flex 2.0
Adobe Flex
Adobe Flex is a software development kit released by Adobe Systems for the development and deployment of cross-platform rich Internet applications based on the Adobe Flash platform...
The Adobe Flash Player is software for viewing multimedia, Rich Internet Applications and streaming video and audio, on a computer web browser or on supported mobile devices. Flash Player runs SWF files that can be created by the Adobe Flash authoring tool, by Adobe Flex or by a number of other...
. ActionScript 3.0 was a fundamental restructuring of the language, so much so that it uses an entirely different virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
The Adobe Flash Player is software for viewing multimedia, Rich Internet Applications and streaming video and audio, on a computer web browser or on supported mobile devices. Flash Player runs SWF files that can be created by the Adobe Flash authoring tool, by Adobe Flex or by a number of other...
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 for hardware acceleration (DirectX
DirectX
Microsoft DirectX is a collection of application programming interfaces for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with Direct, such as Direct3D, DirectDraw, DirectMusic, DirectPlay,...
OpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL...
).
The update to the language introduced several new features:
Compile-time and run-time type 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.
A Java package is a mechanism for organizing Java classes into namespaces similar to the modules of Modula. Java packages can be stored in compressed files called JAR files, allowing classes to download faster as a group rather than one at a time...
A namespace is an abstract container or environment created to hold a logical grouping of unique identifiers or symbols . An identifier defined in a namespace is associated only with that namespace. The same identifier can be independently defined in multiple namespaces...
Bytecode, also known as p-code , is a term which has been used to denote various forms of instruction sets designed for efficient execution by a software interpreter as well as being suitable for further compilation into machine code...
, incompatible with ActionScript 1.0 and 2.0 bytecode
Bytecode
Bytecode, also known as p-code , is a term which has been used to denote various forms of instruction sets designed for efficient execution by a software interpreter as well as being suitable for further compilation into machine code...
A Java package is a mechanism for organizing Java classes into namespaces similar to the modules of Modula. Java packages can be stored in compressed files called JAR files, allowing classes to download faster as a group rather than one at a time...
DOM events allow event-driven programming languages like JavaScript, JScript, ECMAScript, VBScript and Java to register various event handlers/listeners on the element nodes inside a DOM tree, e.g. HTML, XHTML, XUL and SVG documents....
ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known dialects such as JavaScript, JScript, and ActionScript.- History :JavaScript...
ECMAScript for XML is a programming language extension that adds native XML support to ECMAScript . The goal is to provide an alternative to DOM interfaces that uses a simpler syntax for accessing XML documents. It also offers a new way of making XML visible...
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
A run-time system is a software component designed to support the execution of computer programs written in some computer language...
display list for complete control of what gets displayed at runtime.
Completely conforming implementation of the ECMAScript
ECMAScript
ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known dialects such as JavaScript, JScript, and ActionScript.- History :JavaScript...
fourth edition draft specification.
Limited support for dynamic 3D objects. (X, Y, Z rotation, and texture mapping)
Flash Lite
Flash Lite 1.0: 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 also FLV
FLV
Flash Video is a container file format used to deliver video over the Internet using Adobe Flash Player versions 6–11. Flash Video content may also be embedded within SWF files. There are two different video file formats known as Flash Video: FLV and F4V. The audio and video data within FLV files...
video playback.
Flash Lite 4: Added support for Flash 10 ActionScript 3.0 as a browser plugin and also hardware graphics acceleration.
In computer programming, a free-form language is a programming language in which the positioning of characters on the page in program text is not significant. Program text does not need to be placed in specific columns as on old punched card systems, and frequently ends of lines are not significant...
and thus may be created with whichever amount or style of whitespace that the author desires. The basic syntax is derived from ECMAScript
ECMAScript
ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known dialects such as JavaScript, JScript, and ActionScript.- History :JavaScript...
.
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 in pixels), that is 100 pixels wide and high. Then the text parameter 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 named Greeter.as as following.
class com.example.Greeter extends MovieClip
{
public function Greeter {}
public function onLoad:Void
{
var txtHello: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:
var greet:TextField = new TextField;
greet.text = "Hello World";
this.addChild(greet);
Minimal ActionScript 3.0 programs may be somewhat larger and more complicated due to the increased separation of the programming language and the Flash IDE.
Presume the following file to be Greeter.as:
package com.example
{
import flash.text.TextField;
import flash.display.Sprite;
public class Greeter extends Sprite
{
public function Greeter
{
var txtHello:TextField = new TextField;
txtHello.text = "Hello World";
addChild(txtHello);
}
}
}
MXML is an XML-based user interface markup language first introduced by Macromedia in March 2004. Application developers use MXML in combination with ActionScript to develop rich Internet applications, with products such as Adobe Flex....
Adobe Flex is a software development kit released by Adobe Systems for the development and deployment of cross-platform rich Internet applications based on the Adobe Flash platform...
public function initApp:void
{
// Prints our "Hello, world!" message into title
title.text="Hello, World!";
}
]]>
Data types
ActionScript primarily consists of "fundamental" or "simple" data types which are used to create other data types. These data types are very similar to Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
data 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
Boolean - The Boolean data type has only two possible values: true and false or 1 and 0. No other values are valid.
int - The int data type is a 32-bit integer between -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, unsigned integers, and floating-point numbers. The Number data type uses the 64-bit double-precision format as specified by the IEEE Standard for Binary Floating-Point Arithmetic (IEEE-754). values between -9,007,199,254,740,992 (-253) to 9,007,199,254,740,992 (253) can be stored.
String - The String data type represents a sequence of 16-bit characters. Strings are stored internally as Unicode characters, using the UTF-16 format. 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.
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 as associative array
Associative array
In computer science, an associative array is an abstract data type composed of a collection of pairs, such that each possible key appears at most once in the collection....
s that contain key-value pairs, where keys are Strings and values may be any type.
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.)
Vector - A variant of array supported only 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.
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).
flash.display:Sprite - A display object container without a timeline.
flash.display:MovieClip - Animated movie clip display object; Flash timeline is, by default, a MovieClip.
flash.display:Bitmap - A non-animated bitmap display object.
flash.display:Shape - A non-animated vector shape object.
flash.utils:ByteArray - Contains an array of binary byte data.
flash.text:TextField - A dynamic, optionally interactive text field object.
flash.display:SimpleButton - A simple interactive button type supporting "up", "over", and "down" states with an arbitrary hit area.
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.
Function - The core class for all Flash method definitions.
RegExp - A regular expression object for strings.
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 along side standard Flash video (FLV) content.
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:
var yourVariableName:YourVariableType = new YourVariableType(Param1, Param2, ..., ParamN);
So in order to make an empty Object:
var myObject:Object = new Object;
Some types are automatically put in place:
var myString:String = "Hello Wikipedia!"; // This would automatically set the variable as a string.
var myNumber:Number = 5; // This would do the same for a number.
var myObject: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.
var myArray:Array = [5,"Hello!",{a:5, b:7}] //This is the syntax for automatically creating an Array.
//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 between primitive types and reference
Reference (computer science)
In computer science, a reference is a value that enables a program to indirectly access a particular data item, such as a variable or a record, in the computer's memory or in some other storage device. The reference is said to refer to the data item, and accessing those data is called...
types. In ActionScript, all variables are reference types. However, objects that belong to the primitive data types, which includes Boolean, Number, int, uint, and String, have special operators that make them behave as if they were passed by value.
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 (passed by value). 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 (passed by reference).
Some data types can be assigned values with literals
Object literal
In computer science, a literal is a notation for representing a fixed value in source code. Almost all programming languages have notations for atomic values such as integers, floating-point numbers, strings, and booleans; some also have notations for elements of enumerated types and compound...
:
var item1:String="ABC";
var item2:Boolean=true;
var item3:Number=12;
var item4:Array=["a","b","c"];
var item5:Object={name:"Actionscript",version:"3.0"}
var item6:XML = ; //Note that the primitive XML is not quoted
A reference in ActionScript is a pointer to an instance of a class. This does not create a copy but accesses the same memory space. All objects in ActionScript are accessed as references instead of being copied.
var item1:XML=new XML("");
var item2:XML=item1;
item2.firstChild.attributes.value=13;
//item1 now equals item2 since item2 simply points to what item1 points to.
//Both are now:
//
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.
var item1:XML=new XML("");
delete item1;
//If no other reference to item1 is present anywhere else in the application,
//it will be removed on the garbage collector's next pass
ActionScript code protection
Often, Flash developers will decide that while they desire the advantages that Flash affords them in the areas of animation and interactivity, they do not wish to expose their code to the world. However, as with all intermediate language
Intermediate language
In computer science, an intermediate language is the language of an abstract machine designed to aid in the analysis of computer programs. The term comes from their use in compilers, where a compiler first translates the source code of a program into a form more suitable for code-improving...
compiled code, once a .swf file is saved locally, it can be decompiled into its source code and assets. 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, ActionScript obfuscators
Obfuscated code
Obfuscated code is source or machine code that has been made difficult to understand for humans. Programmers may deliberately obfuscate code to conceal its purpose or its logic to prevent tampering, deter reverse engineering, or as a puzzle or recreational challenge for someone reading the source...
have been introduced to solve this problem. Higher-quality obfuscators implement lexical transformations — such as identifier renaming, control flow transformation, and data abstraction transformation — that make it harder for decompilers to generate output likely to be useful to a human. Less robust obfuscators insert traps for decompilers.
