var canPlayAudioFiles = !!(document.createElement('audio').canPlayType);
this is from an HTML5 book, to test whether the browser supports <audio> tag....

I don't understand the '!!' before the parens.... I have never seen this before.. is this jQuery or plain Javascript?
(asking because this line occurs inside a typical jQuery
$(function() {
thingie... )

could this be done with a classic boolean function/method????