X_browser_focus is a project mainly written in JavaScript, it's free.
Get el.hasFocus() and document.activeElement working cross browser
Get access to the getters of of focus management found in the HTML5 spec http://www.w3.org/TR/html5/editing.html#document-level-focus-apis
Place the script node (<script type="text/javascript" src="detect_focus.js"></script>) inside the <head> node or immediately after the opening body tag. We do this as we want to start capturing focus events as soon as possible.
In your Javascript you can feel confident using document.activeElement and element.hasFocus().
var fooEl = document.getElementById('foo');
if(fooEl.hasFocus()){
alert('Yay, foo has focus!');
}
document.addEventListener("focus", function(e){
if(window.console && window.console.log){
console.log(document.activeElement);
}
}, true);We use the focus event listener to log the active element in the example. This seems to be slightly buggy in Webkit browsers using a mouse and clicking. Try tabbing through to see the item update or just look in a browser that supports console.log.
Many thanks to Dirk Ginader (http://blog.ginader.de) for all his help in this.