en.javascript.info/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseleave-table.view/script.js

table.onmouseenter = table.onmouseleave = log;

function log(event) {
  text.value += event.type + ' [target: ' + event.target.tagName + ']\n';
  text.scrollTop = text.scrollHeight;
}