how to display alert when mouse cursor goes out of window

var currentMousePos = { x: -1, y: -1 };
        jQuery(document).mousemove(function(event) {
            currentMousePos.x = event.pageX;
            currentMousePos.y = event.pageY;
        });

jQuery(document).mouseleave(function() {
            var window_width = jQuery(window).width();
            var window_height = jQuery(window).height();

            if((currentMousePos.x < window_width) && (currentMousePos.y > 50))
                return true;
           alert(currentMousePos.x.toString());

        })

Replace alert message with your popup window or fancy box