1.

<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
    <style>
        body{
            user-select:none;
        }
        ul,li{list-style: none;margin:0;padding: 0;}
        .tabs{width:500px;margin:0 auto;background: #d69b9b;color: #fff;padding: 0 20px;}
        .tabs-cell{margin: 20px 0;}
        .tabs-cell ul{display: none;}
        .tabs-cell-2{margin-left: 45px;}
        .tabs-cell-2 li{padding: 7px 0;background: gainsboro;margin: 4px 0;}
    </style>
</head>
<body>
    <div class="tabs">
        <div class="tabs-cell">
            <div>菜单一</div>
            <ul>
                <li class="tabs-cell tabs-cell-2">
                    <div>菜单一一</div>
                    <ul >
                        <li>1-1-1</li>
                        <li>1-1-2</li>
                        <li>1-1-3</li>
                        <li>1-1-4</li>
                        <li>1-1-4</li>
                    </ul>
                </li>
                <li class="tabs-cell tabs-cell-2">
                    <div>菜单一二</div>
                    <ul>
                        <li>1-2-1</li>
                        <li>1-2-2</li>
                        <li>1-2-3</li>
                        <li>1-2-4</li>
                    </ul>
                </li>
                <li class="tabs-cell tabs-cell-2">
                    <div>菜单一三</div>
                    <ul>
                        <li>1-3-1</li>
                        <li>1-3-2</li>
                        <li>1-3-3</li>
                        <li>1-3-4</li>
                    </ul>
                </li>
            </ul>
        </div>
        <div class="tabs-cell">
            <div>菜单二</div>
            <ul>
                <li class="tabs-cell tabs-cell-2">
                    <div>菜单二一</div>
                </li>
                <li class="tabs-cell tabs-cell-2">
                    <div>菜单二二</div>
                    
                </li>
                <li class="tabs-cell tabs-cell-2">
                    <div>菜单二三</div>
                    
                </li>
            </ul>
        </div>
        
    </div>
    <script>
        var  cell=document.getElementsByClassName('tabs-cell')
        var tabs=document.getElementsByClassName('tabs')[0]
        for(var i=0;i<cell.length;i++){
            cell[i].flag=true;
            cell[i].onclick=function(ev){
                isShow(this)
                ev.stopPropagation()
            }
        }

        function isShow(obj){

            var  children=obj.parentNode.children
            for (var i = 0; i < children.length; i++) {
/*                var ul=children[i].getElementsByTagName('ul')[0];
                ul.style.display='none'*/
                var ul=children[i].getElementsByTagName('ul');
                for (var k = 0; k < ul.length; k++) {
                    ul[k].style.display='none'
                }
                
                
                if(children[i]!=obj){//改变this上下相邻元素的开关状态
                    children[i].flag=true;
                }
            }

        
            if(obj.flag){
                obj.getElementsByTagName('ul')[0].style.display='block'
                
            }else{
                obj.getElementsByTagName('ul')[0].style.display='none'
                
            }

            obj.flag=!obj.flag
                
        }

 

//实现原理:获取当前元素之后，然后在获取它的父元素，再获取父元素的所有子元素，最后遍历判断每一个子元素是不是当前元素，不是就将它的字体颜色设置为红色，就这么简单。
    </script>
</body>
</html>