SWFObject Interview Preparation Guide

SWFObject (originally FlashObject) is an open-source JavaScript library used to embed Adobe Flash content onto Web pages, which is supplied as one small JavaScript file. The library can also detect the installed Adobe Flash Player plug-in in all major web browsers, on all major operating systems (OS), and can redirect the visitor to another webpage or show alternate HTML content if the installed plug-in is not suitable.

SWFObject provides a reliable method of embedding Flash content into a webpage by internally handling the various practices that one must follow in order for different web browsers to display Flash content correctly, and isolating them from the web designer. The developer may interface with the library in a standardized manner, the minimum being a single line of JavaScript code. Therefore even inexperienced web designers without knowledge of the ideal HTML code to embed Flash content, can easily insert Flash content into web pages, and have them reliably work for the widest possible audience (excepting those with JavaScript disabled). Flash content inserted using SWFObject will also work on devices that support JavaScript execution (and Flash Player), such as the Wii, PlayStation 3 and Nokia N800, unlike the PlayStation Portable.

SWFObject also includes a few utility functions within its API to retrieve Flash Player related information, such as checking whether a specific version of Flash Player is installed, and a few DHTML utilities to help work with the DOM. Because of this, the most common reasons Flash Website developers turn to external JavaScript frameworks such as jQuery or Prototype are satisfied internally, giving developers fewer reasons to add additional JavaScript libraries to their website.

The library can also be used to integrate Flash Player Express Install into the webpage, allowing users to install the latest Flash Player without leaving the site, although this requires a browser restart.

SWFAddress is a JavaScript and ActionScript library that allows Flash websites to support deep linking, and can automatically integrate with SWFObject.

SWFFit (formerly known as FitFlash) is a JavaScript library used to resize Flash movies according to the browser window size, keeping it accessible independent of the screen resolution. SWFFit primarily configures the web browser to display scroll bars when content exceeds the browser window size. It can also be used to dynamically resize the Flash movie size. It is used together with SWFObject.

The following technique is also known as Full Browser Flash:

Set both the width and height of your SWF to 100% in your SWFObject definition
Include CSS to get rid of any default margins/padding and set the height of the html element, the body element and the entire chain of block level HTML elements that your SWF will be nested in to 100%, because Firefox (or: any Gecko based browser) in standards compliant mode (or: using a valid DOCTYPE) interprets percentages in a very strict way (to be precise: the percentage of the height of its parent container, which has to be set explicitly):

<style type="text/css" media="screen">
html, body, #containerA, #containerB { height:100%; }
body { margin:0; padding:0; overflow:hidden; }
</style>

Manage the scaling and alignment of your SWF and the positioning of your SWF's elements, within your ActionScript code, e.g.:

stage.scaleMode = StageScaleMode.NO_SCALE;
stage.align = StageAlign.TOP_LEFT;

stage.addEventListener(Event.RESIZE, resizeHandler);

function resizeHandler(event:Event):void {
// center stuff
}

When an install gets corrupted (very often caused by corrupt installers) it is impossible to read the Flash Player version number externally using scripting languages. When using dynamic publishing this results in the display of alternative content, with static publishing we let the object element do its job (it decides whether to show Flash content or alternative content based on its built-in MIME type mechanism) which results in the display of Flash content.

In the past years there have been several occasions where a Flash Player didn't expose the right version number externally - as can be retrieved with JavaScript -, caused by corrupt Flash Player Mac OS X installers, affecting Firefox, Opera and Safari on Mac OS X, and also all JavaScript detection scripts, including SWFObject 2, SWFObject 1.5, UFO and the Adobe Flash Player Detection Kit.

Known erroneous versions are (major.minor.release version):

9.0.47 exposes 9.0.19
8.0.24 exposes 8.0.23
9.0.115 exposes either 9.0.47 or 9.0.64 (Note: only Adobe Express Install installers, affecting Firefox on Mac OS X only)

Including a closing </base> tag will prevent this bug in Internet Explorer being triggered. Because for HTML 4 compliant pages (a closing base tag is forbidden under HTML 4), you could use Internet Explorer conditional comments to keep your HTML valid and still include a closing base tag for HTML 4 documents:

<base href="http://www.yourdomain.com/"><!--[if IE]></base><![endif]-->

A In order to make fscommand work in Internet Explorer Adobe recommends to add a block of VBScript to capture and forward the FSCommand calls to JavaScript. However VBScript doesn't work anymore when a Flash movie is inserted using innerHTML or outerHTML, as SWFObject's dynamic publishing method does.

Fortunately you can also use JavaScript instead of VBScript to catch the fscommand calls. A small downside is that it uses proprietary attributes (which, again, wrapped in conditional comments will keep your code valid). E.g. the following block of VBScript code:

<SCRIPT LANGUAGE=VBScript>
on error resume next
Sub myCom_FSCommand(ByVal command, ByVal args)
call myCom_DoFSCommand(command, args)
end sub
</SCRIPT>

Can be replaced with:

<!--[if IE]>
<script type="text/javascript" event="FSCommand(command,args)" for="myCom">
myCom_DoFSCommand(command, args);
</script>
<![endif]-->