Support for the SVGTests interface has just landed in Firefox. It’s currently available in Nightlies and all being well, should make its release appearance in Firefox 12.
The SVGTests interface allows scripts to check whether additional functionality is supported by a browser. There’s no strict definition of what extensions mean but Firefox currently uses element.hasExtension(“http://www.w3.org/1999/xhtml”) to suggest that foreignObject elements support html content and element.hasExtension(“http://www.w3.org/1998/Math/MathML”) to suggest they also display mathML.
The SVGTests interface also allows the requiredFeatures, requiredExtensions and systemLanguage attributes to be manipulated as if they were arrays using the SVG DOM.