菜鸟教程在线编辑器

 
                <!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
  $("p").on("mouseover mouseout",function(){
    $("p").toggleClass("intro");
  });
});
</script>
<style type="text/css">
.intro
{
font-size:150%;
color:red;
}
</style>
</head>
<body>

<p>Move the mouse pointer over this paragraph.</p>

</body>
</html>
              