window.event alternative in Firefox

Question

I see that window.event or event does not work in Firefox, so I need alternative for this. I don't want to set ANY HTML attributes, just Javascript. I'm within this function and I want to get mouse coordinates from here:

document.onmouseover = function(){
    var mouseX = event.clientX;
    var mouseY = event.clientY;
}

Obviously this won't work in firefox, so I want to know how to do it.

Answer 1

This is the typical approach that you'll find in examples everywhere.

document.onmouseover = function(event) {
    event = event || window.event;

    var mouseX = event.clientX;
    var mouseY = event.clientY;
}

The W3C standard way of retrieving the event object is via the first function parameter. Older IE didn't support that approach, so event will be undefined. The || operator lets us fetch the window.event object in that case.