Question

I don’t appear to be able to use the onkeyup event to detect when modifier keys, specifically the Alt key, is being released, reliably. Sometimes it works, sometimes it doesn’t. Most of the time it doesn’t, though.

My current code is:

document.documentElement.onkeyup = function(e) {
    e = e || window.event;
    if( !e.altKey) {
        // do stuff here
        document.documentElement.onkeyup = null;
    }
}

Possibly related to Prevent default event action not working…? as I’m working in IE9 and the File menu pops up. I do dismiss the menu before attempting to trigger the event, though.

Answer 1

Not directly an answer to your question, but this might help you. It is a very detailed description on how browsers manage keydown/press/up.