event propagation Test (Scroll Event)
window.addEventListener('scroll', function() {});
not fired 
document.addEventListener('scroll', function() {});
not fired
not fired
not fired
not fired
not fired
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box
Scroll Box