An alternative to dragenter and dragleave events that fires each event once. There are two similar pairs of events that track mouse movement: mousein+mouseout and mouseenter+mouseleave. Let's say we're listening for these events on the <body> element. The mouseenter and mouseleave events would fire only when mouse pointer enters or leaves the <body> element itself. The mousein and mouseout events would trigger whenever mouse pointer crosses the border of any child within <body>, with event.target set to the child and the child's parent respectively.