More SWFObject 2.0 examples

I just posted a few more SWFObject 2.0 examples:

  • Plain-vanilla SWF embedding using SWFObject 2.0
  • Using SWFObject 2.0 with ExternalInterface
  • Determining whether a SWF was successfully embedded (returning a boolean in JavaScript)
  • Using SWFObject with an ‘onclick’ event

Update: The SWFObject examples list is now located at


Actionscript, JavaScript, and SCORM

Update: A few months after writing this journal entry, I developed SCORM class files for ActionScript 2 and ActionScript 3 (both require ExternalInterface). Check them out here.

For the last week, I’ve been doggedly attempting to create a hybrid of Flash-to-JavaScript communication techniques for creating cross-browser SCORM-conformant courses that work with almost any version of Flash Player. Today I threw in the towel. Here’s my story.

Some background on SCORM in regards to JavaScript and ActionScript

  • SCORM is a standardized method of communicating between a web-based course and a Learning Management System (LMS).
  • SCORM communication is most commonly handled by JavaScript.
  • A Flash-based course therefore needs to communicate with the JavaScript in an HTML file in order to send SCORM calls to the LMS.

It looks like this:

course communication: AS to JS to LMS

Unfortunately, even though they’re both part of the ECMAScript family, ActionScript and JavaScript cannot natively communicate; a ‘communication system’ has to be installed in each Flash-JavaScript project if you want them to talk. Think of it as needing a cell phone to call your mom because she lives in another part of the country!

[ you > cellphone < mom ]

[ actionscript > communication system < javascript ]

Flash-JavaScript Communication: Old-School Versus New-School

Flash-to-JavaScript communication has long been a heavily-discussed topic. Let me try and get you up to speed on it without getting too technical. Old-School refers to Flash Players v6-7, while New-School refers to Flash Players v8+.

Old-School #1: FSCommand

The first old-school technique is to use FSCommand. FSCommand allows synchronous communication, and is pretty straightforward to implement. It’s arguably the most widely-used old-school method for Flash-JavaScript communication in Flash-based SCORM-conformant online courses. (Wow, that’s a lot of hyphens!) But FSCommand has a huge downside: it isn’t cross-platform. It’s specific to Windows machines, and will fail on Macs and Linux boxes.

Old-School #2: GetURL and SetVariable

The second old-school technique is to use ActionScript’s getURL() coupled with SetVariable in JavaScript. For a while, this technique seemed to be popular with a segment of Flash-based course developers who worked with SCORM. The technique basically works like this:

getURL in ActionScript invokes a function contained in the JavaScript. The JavaScript function contains a reference to the SWF, and invokes a method (function) called ‘SetVariable’ in the SWF.



var myVar2 = "Send me to Flash!";

function myFunction(v){
   var swf = window.document.mySwfId;
   swf.SetVariable("myVariable", myVar2);

//watch() or setInterval() used here to detect
//when variable "myVar" has been updated.

This technique wasn’t very popular because it was hard to implement, could only pass strings (no object, arrays, etc.), and was also asynchronous.

Being asynchronous was probably the biggest sticking point for most people, because it meant you couldn’t return the data from JavaScript into ActionScript right away — no var myVariable = getURL("javascript:'myFunction(\'myVariable\')'");; you had to send your request from ActionScript to JS, then wait for it to come back. This required some ugly tricks such as and setInterval to check if the variable had been updated before you could use it in Flash.

Old-School #3: The Flash-JavaScript Integration Kit

The third old-school technique is to use a proxy SWF and LocalConnection. I believe this was first discussed by the guys at MustardLab, and was turned into a full-blown system — the Flash-JavaScript Integration Kit (FJIK) — by two Macromedia employees. I’ll try and explain this as simply as I can.

First, a few things to note about loading external variables into a SWF:

  1. When a Flash SWF first loads on a page, it’s really easy to pass variables into the SWF from your HTML page using FlashVars.
  2. If an HTML page has two SWFs embedded on it, passing variables between the two SWFs is (relatively) easy using LocalConnection.
  3. Passing variables to a SWF AFTER the SWF has already been embedded to the page is the tricky part.

(Warning: this may be a gross oversimplification to some die-hard coders.)

The main idea behind the FJIK method is to dynamically embed a second SWF to your HTML page whenever you want your original SWF to load a variable from JavaScript. This second SWF is usually referred to as a proxy or gateway SWF. The data is loaded into the second SWF using FlashVars as it gets embedded in the HTML. The data is then transferred from the second SWF to the first SWF using LocalConnection. When the transfer is complete, the second SWF can be deleted.

Sounds reasonable, right? This biggest benefit of the FJIK method is that it isn’t limited to passing strings; it supports passing different variable types, such as objects and arrays. It proved to be a popular technique, but it had a few significant drawbacks: transfer speed (you have to wait for a new SWF and FlashVars to load each time you make a call), the required use of 4 or 5 external files (.as, .js, and .swf) is cumbersome, and — like the getURL method — the data is returned asynchronously. No instant ‘return’ statements.

New-School: ExternalInterface

The new-school technique is to use ExternalInterface, which was specifically designed by Macromedia Adobe to make Flash-JavaScript communication much easier. By most accounts, they did an excellent job — data can now be called from ActionScript and returned from JavaScript synchronously, which means your ActionScript and JavaScript can work as one. The code has some kinks, but generally speaking has worked pretty well.

Back to the point: Why the attempt at a hybrid?

You might ask: Why was I trying to make a hybrid of old and new techniques in the first place? The new-school ExternalInterface method works fine and is super-easy!

Answer: ExternalInterface works fine for people with Flash Player 8 and above. That eliminates the majority of the student population I’m targeting. Yes, I know Flash Players v8-9 are supposed to be ubiquitous, but the IT dept. at my workplace installed Flash Player 7 in early 2005 and hasn’t updated most of the machines since then. Employees have no admin rights on their computers, and therefore way to update Flash without calling IT to come do it. When you have over 5,000 employees, this becomes a big issue. It will be at least a few months before the majority of users get Flash Player upgrades.

I also have a colleague in a similar situation, except his target audience is mostly Mac users! This means FSCommand won’t work for him, and can’t hold him over until his end users get Flash Player upgrades.

Simply put, I was hoping to devise a solution for both our problems: a Flash-JavaScript communication method that doesn’t care what version of Flash you have or what platform you’re using! What a dream, huh?

How I hoped it would work

I wanted to create an abstraction layer that separates the SCORM calls from any particular Flash-JavaScript communication method. I was hoping I could do something as simple as this:


var canDoEI:Boolean = ExternalInterface.available;
getURL("javascript:setCanDoEI(" +canDoEI +")");

function getDataFromJS(v){
      //external interface call
   } else {
      //old-school method


var canDoEI = false;

function setCanDoEI(v){
   canDoEI = v;

function sendDataToFlash(v){
      //external interface call
   } else {
      //SetVariable method

This would have allowed me to use the same function calls in Flash Player v6-7 as in Flash Player v8-9, regardless of what technique was being implemented under-the-hood. However, because ExternalInterface and the FJIK each rely on imported classes, have such different syntax, and aren’t both synchronous (only ExternalInterface is synchronous), it would have been a huge headache to try and cram these very different techniques into one course. Bah humbug.

Why not use getURL/SetVariable instead of FJIK?

Granted, the getURL/SetVariable method is much easier to implement than the FJIK method, but it’s also limited to passing strings, and is asynchronous. The asynchronous nature of the getURL/SetVariable method is the main sticking point for me… it’s really tricky to set up the watchers/intervals needed to detect when the variable has successfully been returned from JavaScript. It doesn’t mix well with the synchronous and much speedier ExternalInterface.

So whatcha gonna do?

Wait until we upgrade to Flash Player 9. Sucks, but it’s a pragmatic choice.

I’m in a unique situation in that our IT dept. only supports Internet Explorer on Windows PCs. So far I’ve been able to use the easy-to-implement (and PC-only) FSCommand. I’ll be the first to admit this is something I’ve never been happy about, but hey, it has been a practical and fully-functioning solution for over 2 years. When I developed my current Flash course interface, I knew ExternalInterface was over the horizon, so I didn’t bother with getURL or the FJIK (which hadn’t been released yet). Little did I know that over 2 years later we’d still be supporting Flash Player 7!

In my own defense, I must say that I haven’t ignored standards and best-practices: everything else I’ve built is been cross-browser and cross-platform, including course content. But my guilt is catching up to me, along with a new crop of Mac users at work! It’s in all of our best interests for me to stop using FSCommand in our SCORM courses. If it weren’t for that stinkin’ Flash Player 7 on our older computers… grrr.

So my plan for now is to develop an ExternalInterface version of our Flash-based course interface, and have it ready for that fateful day when the IT guys tell me Flash Player 9 is up and running on (most of) our machines. Sigh… I was hoping for a happier ending!

Related links

Here are some interesting articles I encountered while doing my research:

Making Actionscript calls from Adobe Captivate

Diagram of languages spoken by each document

Captivate 2.0 doesn’t include the ability directly manipulate Actionscript. This has been problematic for people like myself who have Flash-based ‘players’ that load and unload both Captivate SWFs and Flash SWFs… we often need the Captivate SWF to perform some kind of action when it reaches its end.

In my case, I usually need the loaded Captivate SWF to tell the Flash container — an e-learning course interface — that a simulation has been successfully completed.

The figure on the right illustrates the problem: Captivate only allows developers to make Javascript calls, even though Captivate SWFs are running Actionscript under-the-hood!

Flash SWFs, on the other hand, traditionally use Actionscript. Granted, there’s a long history of Flash-Javascript tricks, but most of them have been very ‘hacky’ and not very robust.

The HTML container doesn’t recognize Actionscript at all; it only speaks Javascript.

The old solution: embedded SWFs

Diagram of languages spoken by each document (includes embedded SWF)

For a long time, the only reliable workaround had been to import a Flash SWF containing Actionscript into Captivate, and carefully place it on a Captivate slide. It works like this:

  1. Create a blank Flash SWF, then type a small amount of Actionscript into a frame script (such as calling function “doSomething()” on frame 1).
  2. In order for the imported SWF’s Actionscript to properly communicate with the Flash container, it must be prefixed with “_root.”; this corrects a scope issue and forces the Captivate movie to send the Actionscript call to its parent. The full line of Actionscript in the blank Flash SWF looks like this:
  3. The container SWF must contain the corresponding function. Something like this:
    function doSomething() {
       //do something
  4. When the Captivate SWF’s play head reaches the frame containing the embedded SWF, any Actionscript contained in that embedded SWF is executed.

Click here to see a functioning sample. You can download a ZIP containing the source files here.

This is a simple solution, but it suffers from scope creep and is difficult to maintain. Who really wants to import a SWF every time they need to make an Actionscript call? I sure don’t. And if you ever want to change your Actionscript code, you need to re-export the SWF from Flash, and update the imported SWF in Captivate. Yuck.

Isn’t there a better way?

What about Javascript?

I got to thinking about it, and wondered (again) “Isn’t there a better way to do this?” Then I remembered two things: That Captivate supports Javascript calls, and that SWFObject — arguably the best way to embed Flash SWFs onto a web page — supports passing Javascript variables to a Flash SWF. What if I could make the Captivate SWF communicate with the Flash container SWF via Javascript and SWFObject?

Sad to say, no dice! SWFObject only passes variables when the Flash container SWF loads. I need to pass variables at various times, not just at ‘onload.’

Even though SWFObject was quickly shot down as a communication method, it got me thinking about Javascript as an alternative. Versions of Flash prior to Flash 8 could handle small snippets of Javascript via GetURL, but the GetURL hack is clumsy at best. I knew I didn’t want to go that route. But hang on a minute… what about Flash 8’s ExternalInterface class? It was designed to make Javascript-to-Actionscript communication a breeze! Having never really used it — it’s only supported in Flash Player 8+ and we’re still stuck supporting Flash Player 7 at the office — I decided to give it a whirl. I quickly created this example using Adobe’s tutorial [link no longer available]. First thoughts: Very intriguing and easy to get up and running, but can this be applied to Captivate SWFs loaded into Flash?

The short answer is… YES!

The new solution: Flash’s ExternalInterface class (Actionscript 2.0)

First I laid out the objectives for my experiment:

  • Make the Captivate SWF call the Actionscript function unload() (located in the Flash SWF) via Javascript
  • No variables would be passed… I wanted to keep things as simple as possible

I began editing the code from the aforementioned Adobe example, and in a few short minutes my proof-of-concept was up and running! I was amazed at how quick and easy it was… ExternalInterface was much easier to use than I anticipated.

Here’s what I did:

Step one: Add two lines of Actionscript code to the Flash container

import flash.external.ExternalInterface;
ExternalInterface.addCallback("unload", this, unloadSWF);

Step two: Add two small Javascript functions to the HTML page

//Detect Flash container movie
function getFlashMovie(movieName) {
   if (navigator.appName.indexOf("Microsoft") != -1) {
      return window[movieName];
   else {
      return document[movieName];

//Function to be called by Captivate
function captivateUnload() {
   //Calls "unload" method established in ExternalInterface Actionscript code

Update: In my subsequent testing, using document.getElementById() works fine in place of the getFlashMovie() function. While some developers warn against using getElementById for grabbing Flash SWFs, my tests — using SWFObject as the embed method — were successful in the following environments: WinXP (FF2, FF3, IE6, IE7, Safari 3) and Mac OS X (Safari 3, FF3, Opera 9.5). You can still use getFlashMovie if you prefer.

Step three: Add the Javascript call captivateUnload() to the Captivate button.

That’s it! Really simple, huh? I must admit I was expecting it to be much more complicated.

How it works

As I mentioned earlier, I’m no expert on the ExternalInterface class, but I’ll try and explain what’s going on here. Let’s work backwards and start with the Javascript call in Captivate. Here are the source files if you’d like to use them.

The Captivate file

Captivate Button OptionsIn my example, I’m using a button to call a Javascript function named captivateUnload(). This Javascript function is located in the HTML file.

The HTML file

Moving to the HTML file, we see two functions. The first function, getFlashMovie(movieName), returns the Flash SWF as a Javascript object. This allows us to add functions to the SWF object. This is critical because Flash’s ExternalInterface class will listen for functions attached to the SWF object.

In my example, the Javascript function captivateUnload() attaches the Javascript function unload() to a SWF named simpleSwfLoader:

function captivateUnload() {

By itself, this script won’t do much. In fact, it will throw an error in your browser if it doesn’t detect the accompanying ExternalInterface Actionscript code in your Flash SWF.

The Flash file

In the Flash file, the first line of Actionscript simply tells Flash to import the ExternalInterface class.

import flash.external.ExternalInterface;

The second line is where the action’s at (no pun intended… well, maybe a little!).

ExternalInterface.addCallback("unload", this, unloadSWF);

ExternalInterface’s addCallback method basically tells Actionscript to start listening for Javascript functions that have been attached to the SWF object. In our scenario, the unload() function has been attached to the SWF object.

The three parameters ("unload", this, unloadSWF) specify exactly what to listen for (a function named “unload”), where to listen (“this” SWF), and what to do when the SWF hears the correct bit o’ Javascript (execute a function named “unloadSWF”).

So for this example, the Flash SWF will execute function unloadSWF() when it hears Javascript call a function named unload() that is attached to a SWF named simpleSwfLoader.

Got all that? I know it sounds confusing (it still makes my head spin a little), but it’s actually pretty straightforward. Here’s a diagram for you visual learners:

Flow of scripting calls

And that’s the whole enchilada.

Let me remind you that this is a very simple example, and I’m sure this technique can be harnessed to do much more! Also, this example uses ExternalInterface for Actionscript 2.0. Flash CS3’s new Actionscript 3.0 uses slightly different code, but the concept is the same.

If any of you find this tutorial useful, or think of new ways to utilize this technique, please let me know by adding a comment.

Thanks, and good luck!

Embedded SWF technique source files  |  ExternalInterface technique source files