In mozilla, event is undefined, IE everything is fine

Question

var mouse = function(e){
    var x = e.pageX || (e.clientX + document.body.scrollLeft);
    var y = e.pageY || (e.clientY + document.body.scrollTop);

    alert(x + " " + y);
};
window.onload = function(e) {
    if(!e) { var e = window.event; }
    mouse(e);
};

This works in IE and I get the proper mouse x and y coordinates. However, when ran in something other then IE I just get an alert "NaN NaN"

(I've tried searching)

Answer 1

To me this looks wrong in many ways. I think you want onmousemove and not onload - possibly document.onmousedown - and you do not want to alert. Instead change some innerHTML or document.title

Do you want the click or the move?

document.onmousemove = function(e){
    var x = e.pageX || (e.clientX + document.body.scrollLeft);
    var y = e.pageY || (e.clientY + document.body.scrollTop);
    document.title=x + " " + y;
};

Also have a look here

Responding to the onmousemove event outside of the browser window in IE

Answer 2

This is because load events in most browsers don't have clientX and clientY properties.

Change your onload function to the following:

window.onload = function (e) {
    if (!e) { 
        var e = window.event; 
    }
    alert("type is " + e.type + " clientX is " + e.clientX);
    mouse(e);
};

and you'll see, for non-IE browsers, that the type is a load event, but clientX is undefined.