<script type="text/javascript" src="/js/jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$(".btn1").click(function(){
<p style="width:200px;height:200px;background-color:yellow">This is a paragraph. <b>Bold</b> and <i>italic</i> text.</p>
<button class="btn1">删除 p 元素的内容</button>