纯css实现多级折叠菜单，折叠树

1、参考自csdn，（https://blog.csdn.net/woshisap/article/details/6679977）为了适应项目，精简其样式并稍作修改，记录在博客里。

2、运用checkbox的checked值来判断下级栏目是否展开，CSS3的选择器中提供了:checked 这个伪类，这个伪类提供我们，当元素拥有checked这个值的时候就执行你的CSS。

当有子菜单时，菜单项右侧有向下的箭头，当收起菜单项时，箭头朝上。图片可以自己替换。

3、效果图

4、代码片段

 <ol class="tree">  
        <li>  
            <label for="folder1" class="folderOne">泽元框架</label> <input type="checkbox" id="folder1" /> 
            <ol>  
                 <li>  
                    <label for="subfolder1"class="folderTwo">开发规范</label> <input type="checkbox" id="subfolder1"  />   
                    <ol>  
                        <li class="file folderThree"><a href="#">常见界面错误举例</a></li>  
                        <li class="file folderThree"><a href="#">关于发行报告对BUG管理提出…</a></li>  
                        <li class="file folderThree"><a href="#">插件内部JAVA包命名规范</a></li>  
                    </ol>  
                </li> 
                 <li class="file folderTwo"><a href="#">概述</a></li>  
                 <li class="file folderTwo"><a href="#">服务器集群</a></li>  
                 <li class="file folderTwo"><a href="#">模板</a></li>  
                 <li class="file folderTwo"><a href="#">安全机制</a></li>   
            </ol>  
  
        </li>  
        <li>  
            <label for="folder2" class="folderOne" >ZCMS</label> <input type="checkbox" id="folder2" />   
            <ol>  
                <li class="file folderTwo"><a href="#">实时数据</a></li> 
                <li>  
                    <label for="subfolder2" class="folderTwo">实时数据</label> <input type="checkbox" id="subfolder2"  />   
                    <ol>  
                        <li class="file folderThree"><a href="#">实时数据</a></li>  
                        <li class="file folderThree"><a href="#">实时数据</a></li>  
                        <li class="file folderThree"><a href="#">实时数据</a></li>  
                    </ol>  
                </li>  
            </ol>  
        </li> 
        <li>  
            <label for="folder3"  class="folderOne">ZAS</label> <input type="checkbox" id="folder3" />   
            <ol>  
                <li class="file folderTwo"><a href="#">实时数据</a></li> 
                <li class="file folderTwo"><a href="#">实时数据</a></li> 
            </ol>  
        </li> 
        <li>  
            <label for="folder4"  class="folderOne">ZHTML标签</label> <input type="checkbox" id="folder4"/>   
            <ol>  
                <li class="file folderTwo"><a href="#">实时数据</a></li> 
                <li class="file folderTwo"><a href="#">实时数据</a></li> 
            </ol>  
        </li> 
        <li>  
            <label for="folder5"  class="folderOne">UI框架API手册</label> <input type="checkbox" id="folder5"/>   
            <ol>  
                <li class="file folderTwo"><a href="#">实时数据</a></li> 
                <li class="file folderTwo"><a href="#">实时数据</a></li> 
            </ol>  
        </li> 
    </ol>  

<style type="text/css">  
    .tree {margin: 0;padding: 0;background-color:#f2f2f2;overflow: hidden;}  
    /*隐藏input*/
    .tree li input{position: absolute;left: 0;opacity: 0;z-index: 2;cursor: pointer;height: 1em;width:1em;top: 0;}  
    /*所有菜单项设置统一样式*/
    .tree li {position: relative;list-style: none;}   
    /*一级菜单加下边线*/
    .tree>li{border-bottom: 1px solid #d9d9d9;}
    /*给有子菜单的菜单项添加背景图标*/
    .tree li label {max-width:999px;cursor: pointer;display: block;margin:0 0 0 -50px;padding: 15px 10px 15px 70px;background: url(../../images/cp-detail-arrow-b.png) no-repeat right center;background-position:95% 50%;white-space:nowrap;overflow:hidden;text-overflow: ellipsis; }  
    .tree li label:hover,li label:focus{background-color:#a7a7a7;color:#fff;}
    /*清除所有展开的子菜单的display*/
    .tree li input + ol{display: none;}  
    /*当input被选中时，给所有展开的子菜单设置样式*/
    .tree input:checked + ol {padding-left:14px;height: auto;display: block;}  
    .tree input:checked + ol > li { height: auto;}  
    /*末层菜单为A标签，设置样式*/
    .tree li.file a{margin:0 -10px 0 -50px;padding: 15px 20px 15px 70px;text-decoration:none;display: block;color:#333333;white-space:nowrap;overflow:hidden;text-overflow: ellipsis;} 
    .tree li.file a:hover,li.file a:focus{background-color:#a7a7a7;color:#fff;} 
    /*不同层级的菜单字体大小不同*/
    .tree .folderOne{font-size: 18px;}
    .tree .folderTwo{font-size:16px;}
    .tree .folderThree{font-size:14px;}
</style>  

 <script type="text/javascript">
		$(document).ready(function() {
            //每个有子菜单的菜单项添加点击事件
			$(".tree label").click(function(){
                //获取当前菜单旁边input的check状态
			    var isChecked = $(this).next("input[type='checkbox']").is(':checked');
                //展开和收齐的不同状态下更换右侧小图标
				if(isChecked){
					$(this).css(
						"background-image","url(../images/cp-detail-arrow-b.png)"
					);
				}else{
					$(this).css(
						"background-image","url(../images/cp-detail-arrow-t.png)"
					);
				}
			});
			
		});
	</script>