html：

<div class="sidebar">
    <ul>
        <li>優先順序
             <ul>
                <li><aonclick=""class="sidebar-selected">全部</a></li>
                <li><aonclick="">P1</a></li>
                <li><aonclick="">
 
P2</a></li>
                <li><aonclick=“" >P3</a></li>
                <li><aonclick="">P4</a></li>
            </ul>
        </li>
    </ul>
</div>

css：

.sidebar {
    border-right: 1px solid #f0f2f1;
    width: 180px;
    float
 
: left;
    padding-left: 35px;
}

.sidebar>ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.sidebar>ul>li {
    font-size: 18px;
    font-weight: 400;
    padding: 0010px;
    margin-top: 5px;
}

.sidebar>ul>li>ul {
    border-top: 1px dashed rgba(0,0,0,0.1);
    display: block;
    list-style
 
: none;
    margin: 5px010px0;
    padding: 10px0010px;
    font-size: 14px;
    max-height: 138px;
    overflow: auto;
}

.sidebar a {
    line-height: 1.5;
}

.sidebar a:hover {
    color: #e74430;
    cursor:pointer;
}

.sidebar-selected {
     color: #e74430;
}