单击子菜单时，该菜单必须始终处于活动状态

Question

对不起，我在子菜单页面上找不到JavaScript教程来创建带有活动子菜单的菜单

<ul class="sidebar-menu collapsible collapsible-accordion" data-collapsible="accordion">
        <li class="no-padding active"><a class="waves-effect waves-grey active" href="A"><i class="material-icons">settings_input_svideo</i>A</a></li>
        <li class="no-padding">
            <a class="collapsible-header waves-effect waves-grey"><i class="material-icons">equalizer</i>B<i class="nav-drop-icon material-icons">keyboard_arrow_right</i></a>
            <div class="collapsible-body">
                <ul>
                    <li><a href="A1">A1</a></li>
                    <li><a href="A2">A2</a></li>
                    <li><a href="A3">A3</a></li>
                    <li><a href="A4">A4</a></li>
                </ul>
            </div>
        </li>
        <li class="no-padding">
            <a class="collapsible-header waves-effect waves-grey"><i class="material-icons">loyalty</i>C<i class="nav-drop-icon material-icons">keyboard_arrow_right</i></a>
            <div class="collapsible-body">
                <ul>
                    <li><a href="C1">C1</a></li>
                    <li><a href="C2">C2</a></li>
                </ul>
            </div>
        </li>

  

当活动的 li 显示类“无填充活动”时，    a 类“波效应波-灰色有效”

     

当当前子菜单出现时， li 类“无填充活动”和 a   类“可折叠标头波-效果波-灰色有效”和 li a   类“活动页面”