将Sub-Sub-Menus添加到带有子菜单的CSS菜单中

<ul class="menu">
  <li><a href="#">菜单1</a>
    <ul class="submenu">
      <li><a href="#">子菜单1</a></li>
      <li><a href="#">子菜单2</a></li>
      <li><a href="#">子菜单3</a>
        <ul class="subsubmenu">
          <li><a href="#">子子菜单1</a></li>
          <li><a href="#">子子菜单2</a></li>
          <li><a href="#">子子菜单3</a></li>
        </ul>
      </li>
    </ul>
  </li>
  <li><a href="#">菜单2</a></li>
  <li><a href="#">菜单3</a></li>
</ul>

.menu {
  list-style: none;
  padding: 0;
  margin: 0;
}

.menu li {
  position: relative;
}

.menu a {
  display: block;
  padding: 10px;
  background: #f0f0f0;
  color: #333;
  text-decoration: none;
}

.menu .submenu {
  display: none;
  position: absolute;
  top: 0;
  left: 100%;
}

.menu .subsubmenu {
  display: none;
  position: absolute;
  top: 0;
  left: 100%;
  min-width: 100%;
}

.menu li:hover > .submenu {
  display: block;
}

.menu .submenu li:hover > .subsubmenu {
  display: block;
}