event.target 属性返回哪个 DOM 元素触发了事件。

<ul>
  <li>list <strong>item 1</strong></li>
  <li><span>list item 2</span></li>
  <li>list item 3</li>
</ul>

<script>
$("ul").click(function(event) {
  console.log(event);	
  var $target = $(event.target);
  if ( $target.is("li") ) {
    $target.css("background-color", "red");
  }
});
</script>
<ul>
  <li>list <strong>item 1</strong>