JS树结构的使用
1. 下面是一种简单的树结构，使用的是jquery插件，需要先导入下面两个js文件
<script type="text/javascript" src="js/jquery.tree.js"></script>
<script type="text/javascript" src="js/jquery.tree.checkbox.js"></script>
<script type="text/javascript">
$(function () {
$("#demo_1").tree({
ui : {
theme_name : "checkbox"
},

plugins : {
checkbox : { }
}
});
});
</script>
<div class="demo" id="demo_1">

<ul>
<li id="1000" title="本市" class="open"><a href="#"><ins>&nbsp;</ins>本市</a>
<li id="2000" title="环京六省市" class="open"><a href="#"><ins>&nbsp;</ins>环京六省市</a>
     <ul>
<li id="2001" title="河北(环京)" class="open"><a href="#"><ins>&nbsp;</ins>河北(环京)</a></li>
<li id="2002" title="辽宁(环京)" class="open"><a href="#"><ins>&nbsp;</ins>辽宁(环京)</a></li>
<li id="2003" title="内蒙(环京)" class="open"><a href="#"><ins>&nbsp;</ins>内蒙(环京)</a></li>
<li id="2004" title="山东(环京)" class="open"><a href="#"><ins>&nbsp;</ins>山东(环京)</a></li>
<li id="2005" title="山西(环京)" class="open"><a href="#"><ins>&nbsp;</ins>山西(环京)</a></li>
<li id="2006" title="天津(环京)" class="open"><a href="#"><ins>&nbsp;</ins>天津(环京)</a></li>
   </ul>
</li> 
<li id="3000" title="公安部" class="open" ><a href="#"><ins>&nbsp;</ins>公安部</a>   
      <ul>
<li id="3002" title="天津(公安部)" class="open" ><a href="#"><ins>&nbsp;</ins>天津(公安部)</a></li>
<li id="3003" title="河北(公安部)" class="open" ><a href="#"><ins>&nbsp;</ins>河北(公安部)</a></li>
<li id="3004" title="山西(公安部)" class="open" ><a href="#"><ins>&nbsp;</ins>山西(公安部)</a></li>
<li id="3005" title="内蒙古(公安部)" class="open" ><a href="#"><ins>&nbsp;</ins>内蒙古(公安部)</a></li>
<li id="3006" title="辽宁(公安部)" class="open" ><a href="#"><ins>&nbsp;</ins>辽宁(公安部)</a></li>
<li id="3007" title="吉林" class="open" ><a href="#"><ins>&nbsp;</ins>吉林</a></li>
<li id="3008" title="黑龙江" class="open" ><a href="#"><ins>&nbsp;</ins>黑龙江</a></li>
<li id="3009" title="上海" class="open" ><a href="#"><ins>&nbsp;</ins>上海</a></li>
<li id="3010" title="江苏" class="open" ><a href="#"><ins>&nbsp;</ins>江苏</a></li>
<li id="3011" title="浙江" class="open" ><a href="#"><ins>&nbsp;</ins>浙江</a></li>
<li id="3012" title="安徽" class="open" ><a href="#"><ins>&nbsp;</ins>安徽</a></li>
<li id="3013" title="福建" class="open" ><a href="#"><ins>&nbsp;</ins>福建</a></li>
<li id="3014" title="江西" class="open" ><a href="#"><ins>&nbsp;</ins>江西</a></li>
<li id="3015" title="山东(公安部)" class="open" ><a href="#"><ins>&nbsp;</ins>山东(公安部)</a></li>
<li id="3016" title="河南" class="open" ><a href="#"><ins>&nbsp;</ins>河南</a></li>
<li id="3017" title="湖北" class="open" ><a href="#"><