How can I detect when the mouse leaves the window?

Matt picture Matt · May 28, 2009 · Viewed 106k times · Source

I want to be able to detect when the mouse leaves the window so I can stop events from firing while the user's mouse is elsewhere.

Any ideas of how to do this?

Answer

J Mills picture J Mills · Jul 6, 2010

Please keep in mind that my answer has aged a lot.

This type of behavior is usually desired while implementing drag-drop behavior on an html page. The solution below was tested on IE 8.0.6, FireFox 3.6.6, Opera 10.53, and Safari 4 on an MS Windows XP machine.
First a little function from Peter-Paul Koch; cross browser event handler:

function addEvent(obj, evt, fn) {
    if (obj.addEventListener) {
        obj.addEventListener(evt, fn, false);
    }
    else if (obj.attachEvent) {
        obj.attachEvent("on" + evt, fn);
    }
}

And then use this method to attach an event handler to the document objects mouseout event:

addEvent(document, "mouseout", function(e) {
    e = e ? e : window.event;
    var from = e.relatedTarget || e.toElement;
    if (!from || from.nodeName == "HTML") {
        // stop your drag event here
        // for now we can just use an alert
        alert("left window");
    }
});

Finally, here is an html page with the script embedded for debugging:

<html>
<head>
<script type="text/javascript">
function addEvent(obj, evt, fn) {
    if (obj.addEventListener) {
        obj.addEventListener(evt, fn, false);
    }
    else if (obj.attachEvent) {
        obj.attachEvent("on" + evt, fn);
    }
}
addEvent(window,"load",function(e) {
    addEvent(document, "mouseout", function(e) {
        e = e ? e : window.event;
        var from = e.relatedTarget || e.toElement;
        if (!from || from.nodeName == "HTML") {
            // stop your drag event here
            // for now we can just use an alert
            alert("left window");
        }
    });
});
</script>
</head>
<body></body>
</html>