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Monday, November 22, 2010

Jangaroo 0.7.12: More AS3 Features, even for IE9

What's new in Jangaroo 0.7.12?

We are proud to present our latest Jangaroo release with many improvements and new features in several different areas.
Our last blog post is a while ago, but in the meantime, we delivered several intermediate releases and used light-weight Twitter announces (just follow @Jangaroo).


  • github
    Jangaroo is on github now!
    Check out Jangaroo Tools (compiler, Maven plugins, IDEA plugin) from
    Find Jangaroo JavaScript wrapper APIs (browser API, Ext JS, CKEditor, soundmanager 2) and libraries (URI utils, JooUnit, JooFlash) at
  • Maven Central
    Since version 0.7.9 you can use Jangaroo from Maven without specifying any <repository> or <pluginRepository> now, so the POMs get even simpler. This is possible because all new Jangaroo Maven artifacts are deployed to Maven Central. Sonatype kindly offers this service to all Open Source projects. The old Jangaroo Maven repository still exists to host the old versions.
  • Compiler and Runtime Version in Generated Code
    The compiler now adds version information, so that the Jangaroo Runtime can check compatibility of generated JavaScript code. A class runtimeApiVersion/compilerVersion is compatible with the current Runtime if

    • the runtimeApiVersion matches the Runtime's runtimeApiVersion exactly and
    • the compilerVersion is lower or the same as the Runtime's compilerVersion.
    The idea is that runtimeApiVersion is only incremented when the contract between compiler and runtime changes. Thus, you may use library code compiled with an older compiler together with a runtime plus your code compiled with a later compiler. This may be important if you want to use a library and a new compiler feature, but the library is not yet available compiled with the latest compiler version. As long as we release all Jangaroo libraries ourselves, this may be academic, but this situation is bound to change sooner or later.
  • Cyclic Static Dependency Detection
    The Runtime now logs a warning if a cyclic static initializer dependency is detected. This happens if one class triggers initializing another class and the other class directly or indirectly triggers initializing the first class, which is already in progress. This situation does not have to cause problems, but the first class is already used while it is not yet fully initialized, so e.g. members might still be "undefined". Clean code should not contain such initialization cycles.
  • IntelliJ IDEA 9 Plugin
    As always, the Jangaroo Language IDEA plugin has been updated to use the latest compiler. In IDEA, simply go to Settings | Plugins | Available, search for Jangaroo Language, and click the "Download & Install" or "Update Plugin" button. After restarting IDEA, you can import Jangaroo Maven projects and enjoy code completion, fast compile-and-deploy turn-around ("Make Project"), and instant static type checking.

Newly Supported AS3 Features

  • Full trace() Compatibility and More
    In previous Jangaroo versions, trace() only took a single parameter to print to the JavaScript console. However, in AS3, trace takes arbitrary parameters and joins them to a string (using space as separator). We now implement exactly this method signature and semantics.
    To also take advantage of Firebug's different console log levels, indicated through icons, without changing the method signature, we use the following convention: If you start your trace output with one of [LOG], [INFO], [WARN] or [ERROR], the corresponding Firebug console method (log(), info(), warn() or error()) is invoked with the remainder of the message. For other environments, the string is printed as-is.
  • Variable Default Values
    Depending on their type, class variables (fields) are initialized to standard values as defined in the AS3 language specification (see bottom of page). Note that this feature is only implemented for class variables, including statics, but not yet for local variables.
  • Helper Classes
    Out-of-package helper classes, i.e. non-public class definitions contained in the source file of a public class, are now fully supported. Unfortunately, I could not find any official Adobe reference documentation on helper classes, so please refer e.g. to this blog post on helper classes .
  • Annotations
    Basic support for annotations, i.e. meta data in square brackets added to classes or methods, has been added to the Jangaroo compiler and runtime. Since we do not yet fully implement flash.utils.describeType(), the only way to query meta data at runtime is through a Jangaroo-specific API which is subject to change. If you want to give it a try, find the meta data for a class using the following code:
    var metadata:Object =
    To retrieve the metadata of a public class member, use the following pattern:
    var memberMetadata:Object =
      .getMemberDeclaration("public", "someMember").metadata;
    In both cases, the according annotation is transformed to an Object straight-forwardly, e.g.
    [SWF(width=465, height=465,
         backgroundColor=0, frameRate=15)]
    results in the metadata object
    {SWF:{width:465, height:465,
          backgroundColor:0, frameRate:15}}
  • as Operator
    Jangaroo has been supporting as for quite some time, but so far, it was not transformed into any code (only comments in debug mode).
    Now, as is implemented with its original AS3 semantics, i.e. checking the object's type and evaluating to null if there is no match. Be aware that this changes semantics of your code, for example if you used as to cast to a type to call some method, which might have worked at runtime without the object actually being an instance of the type. In such cases, you can fall back to the type cast syntax (Type(expr)), which still generates comments only. Be warned that this code might someday throw a TypeError when using a later Jangaroo release.

Browser Compatibility

  • trace() in IE
    trace() now also works with Internet Explorer's console. It already worked before with Firefox with Firebug, WebKit, Opera, and any browser using Firebug light.
  • Property Accessor Functions in IE9
    So far, Jangaroo supported AS3 properties (function get/set) in WebKit, Firefox and Opera, but not in any version of Internet Explorer. IE9 is the first to implement custom properties accessor functions for any JavaScript object. IE8 already introduced the ECMAScript 5 methods to define properties, but they were only implemented for DOM objects. Thus, Jangaroo only supports property accessor functions in IE9.
    To simulate this feature also in older IE versions is a much harder task, but still we might tackle it later (see discussion on Jangaroo User Group).
  • Workaround for IE9 Crash
    Jangaroo stores class meta data under the expando property $class of the class's constructor function. Even for built-in classes, when used from Jangaroo code, the Runtime attaches this property. So far, this approach worked well with IE, but IE9 beta crashed (!) when trying to run our Box2D demo.
    After intensive debugging, I figured out that IE9 does not like the $class property of built-in class TypeError being accessed. With some more digging into, the real source revealed itself: If in IE9 document mode, you set any expando property on the built-in Error class and query it through a subclass (like TypeError), IE9 beta crashes. Comprising only 21 characters, this might actually be the shortest JavaScript "code of death" for IE9:
    The workaround for Jangaroo is not to set $class on the Error class, but Microsoft will have to fix this bug anyway, or there will be lots of Websites with links that say: "To crash IE9, please click here."
  • @-Properties in IE
    Respect that IE does not like properties starting with @, and quote them.

Bug Fixes, Improvements and API Changes

  • fixed a minor bug in regular expressions syntax and improved parser error messages
  • improved class initialization, which was sometimes triggered eagerly when not necessary
  • cleaned up Runtime logging in debug mode: log class initialization instead of class loading
  • Introduced joo.boundMethod() in favor of Function.prototype.bind(). See its ASDoc for details.
  • overhauled joo.ResourceBundleAwareClassLoader API. See its ASDoc for details.

Jangaroo Libraries

Together with a new release of the Jangaroo tools, we always release all Jangaroo libraries, too. Besides being recompiled with the latest compiler version, there are also many updates and new features.
  • Flash Compatibility jooflash
    This library re-implements the Flash APIs in the browser, using HTML5 features like canvas. It is still rather incomplete, but nevertheless suffices for demos like flash-lines as well as quite complex applications like Box2DFlashAS3.
  • Network Utilities jangaroo-net
    This new module contains utilities for URI parsing, formatting, relativizing and resolving functionality according to RFC 3986.
  • Ext JS ActionScript API ext-as
    The library Ext AS is an ActionScript 3 wrapper for Ext JS 3.2.2, so you can do Ext coding with code completion and type checks while keeping a fast turn-around.
  • Many more libraries, which we will cover in a future blog post.

As always, comments, questions, corrections, praise etc. are highly welcome! Why not contribute by issuing pull requests on github to include your bug fixes?

Andreas and Frank