鼠标悬停出菜单

<span class="btn-list-group">
  <a class="btn">悬停</a>
  <span class="btn-list-area">
    <a class="btn">新建</a>
    <a class="btn">编辑</a>
    <a class="btn">打开</a>
    <a class="btn">导出</a>
    <a class="btn">导入</a>
    <a class="btn">退出</a>
  </span>
</span>

.btn-list-group {
    position: relative;
}
.btn-list-area {
    display: none;
    position: absolute;
    left: 0;
    right: 0;
}
.btn-list-group:hover .btn-list-area {
  display: block; 
}
.btn {
    display: inline-block;
    padding: .4em .7em;
    font-size: 14px;
    font-weight: 400;
    color: #6c757d;
    text-align: center;
    line-height: 1.5;
    background-color: #fff;
    border: 1px solid #e9ecef;
    cursor: pointer;
    outline: none;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}