纯css实现树形结构

纯css实现属性结构

**css实现属性结构的思路是利用伪类实现树形结构连接线，如果想实现点击展开和收
缩以及复选框效果还得配合js来实现。其实展开和收缩就是一个点击元素其子元素隐藏
和显示的切换。**

效果图

html结构

    

        

            1级菜单
            

                
2级菜单
                

                    2级菜单
                    

                        
3级菜单
                        
3级菜单
                    
                
            
        
        

            1级菜单
            

                
2级菜单
                
2级菜单
            
        
    

css

        ul.domtree,
        ul.domtree ul {
            margin: 0;
            padding: 0 0 0 2em;
        }

        ul.domtree li {
            list-style: none;
            position: relative;
        }

        ul.domtree>li:first-child:before {
            border-style: none none solid none;
        }

        ul.domtree li:before {
            position: absolute;
            content: '';
            top: -0.01em;
            left: -0.7em;
            width: 0.5em;
            height: 0.615em;
            border-style: none none solid solid;
            border-width: 0.05em;
            border-color: #aaa;
        }

        ul.domtree li:not(:last-child):after {
            position: absolute;
            content: '';
            top: 0.7em;
            left: -0.7em;
            bottom: 0;
            border-style: none none none solid;
            border-width: 0.05em;
            border-color: #aaa;
        }