html(content)为匹配的元素设置传入的HTML代码块内容

node2:/var/www/html/js#cat h34.html 
<a>11111</a>
<div>222222</div>
<p>ddddddd</p>
<a>测试</a>
<script type="text/javascript" src="jquery-2.2.2.min.js"></script> 
<script type="text/javascript" src="h34.js"></script>
node2:/var/www/html/js#
node2:/var/www/html/js#cat h34.js
//$('a').css("background","red")
$('a').html('<div id="message"></div>');