<script type="text/javascript" src="/js/jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$("button").click(function(){
$("#span1").text(x.left);
<p>本段落的偏移是 <span id="span1">unknown</span> left 和 <span id="span2">unknown</span> top。</p>
<button>获得 offset</button>