Checking if browser is in fullscreen

Question

Is there a way to check if a browser is currently in fullscreen mode (after the user pressed f11)?

Something like:

if (window.fullscreen) {
  // it's fullscreen!
}
else {
  // not fs!
}

Thanks.

Steerpike's answer is pretty good, but my comment:

Thanks a lot, but this answer is not sufficient for FF. In Chrome I can set a small tolerance, but in FF the urlbar and tabs takes a while to disappear, which means after pressing f11, the detected window.innerWidth is still too small.

Answer 1

if(window.innerWidth == screen.width && window.innerHeight == screen.height) {

} else {

}

(Warning: The browser chrome may muck with the height comparisons but the width checks should be pretty spot on)

Answer 2

In Firefox 3, window.fullScreen works (https://developer.mozilla.org/en/DOM/window.fullScreen).

So, you could potentially do something like this:

if((window.fullScreen) ||
   (window.innerWidth == screen.width && window.innerHeight == screen.height)) {

} else {

}