WAI-ARIA: Javascript Capability Testing?

In the spirit of progressive enhancement, I'd like开发者_开发问答 to do some ARIA capabilities testing to implement additional enhancements if they're supported by the browser. I'm not looking to detect screen readers—I'm looking to ensure that screen reader users will get the optimal experience given the tools that they're using.

For example, if the aria-live attribute is not supported, then it may not be a good idea to implement endless scrolling.

I'm aware that there's an additional concern that browsers may support these attributes but the screen reader may not. Since screen readers run transparently over browsers, I'm okay with that edge case being ignored.

I've never heard of anyone doing anything like this. Is it as easy as testing for additional DOM properties endowed by browsers? Do one of Mark Pilgrim's other capability testing techniques work here?

Thanks!

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The first answer has some incorrect information. Certain browsers do support WAI-ARIA and some don't. Browsers send events to screen readers via the operating system's accessibility API. If you use IE 7, for example, it cannot deal with WAI-ARIA where IE 8 can. Look at this graphic

That being said, you can't do testing to determine what tags are supported. In general, limited WAI-ARIA support began in FF2 and IE8. Look at the release notes of the browser to determine what WAI-ARIA support it has.

Here is a link that details testing WAI-ARIA

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I'm not looking to detect screen readers

I'm sorry, but that's exactly what you're looking to do. It is not possible to detect screen readers unless they expose themselves to content scripts in some way, and there are many different screen readers, so you shouldn't really try. If anything, you might be able to get some hack working in browsers that support aural CSS to detect screen readers, but you're definitely not going to be able to detect if a certain ARIA feature is supported or not.

if the aria-live attribute is not supported

No browsers actually "support" ARIA more than just providing element property accessors in the DOM; only screen readers/assistive reading software supports ARIA, in that it actually uses the ARIA attributes to help the user interact with a website.

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As mentioned in @ChrisMorgan’s comment, Derek Featherstone’s A List Apart article on the difficulties of implementing ARIA gracefully is a must-read.