如何用CSS实现可无限嵌套的响应式导航菜单（无需新增选择器）

以下是修改后的完整代码，实现无需新增CSS选择器即可添加任意层级子菜单的功能，子菜单展开效果符合要求：

HTML 结构 #

<div class="logo" role="img">
  <img src="Images/Logo.png" height="100" style="width:auto; float:left;" />
</div>
<header class="header">
  <div class="nav-menu-button">
    <div class="nav-menu-line"></div>
  </div>
  <nav class="nav" data-visible="false" role="navigation">
    <ul>
      <li>
        <a href="#">Home</a>
      </li>
      <li class="has-submenu">
        <a href="#">Goods</a>
        <button class="submenu-toggle" aria-expanded="false">▼</button>
        <ul class="submenu">
          <li><a href="#">Category 1</a></li>
          <li class="has-submenu">
            <a href="#">Category 2</a>
            <button class="submenu-toggle" aria-expanded="false">▼</button>
            <ul class="submenu">
              <li><a href="#">Subitem 1</a></li>
              <li><a href="#">Subitem 2</a></li>
            </ul>
          </li>
        </ul>
      </li>
      <!-- 可直接复制以下结构添加更多层级子菜单 -->
      <!--
      <li class="has-submenu">
        <a href="#">父菜单</a>
        <button class="submenu-toggle" aria-expanded="false">▼</button>
        <ul class="submenu">
          <li><a href="#">子菜单</a></li>
        </ul>
      </li>
      -->
    </ul>
  </nav>
</header>

CSS 样式 #

@font-face {
  font-family: "Roboto";
  font-style: normal;
  src: url("../Fonts/Roboto.ttf") format("truetype");
}

* {
  font-family: "Roboto";
  font-size: 20px;
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  direction: rtl;
}

.logo {
  z-index: 10;
  position: relative;
}

.header {
  background: linear-gradient(to top, #9472ff 2%, #3d00ff 98%) center/100%;
  border-radius: 10px;
  box-shadow: 1px 2px 4px #000000;
  color: white;
  width: 100%;
  height: 100px;
  padding-right: 10px;
  padding-top: 40px;
  text-align: right;
  text-shadow: 0px 2px 2px #000000;
}

/* 基础导航样式调整 */
.nav {
  list-style: none;
  display: flex;
  gap: 24px;
}
.nav ul {
  list-style: none;
  width: 100%;
}
.nav li {
  position: relative;
  width: 100%;
  text-align: center;
}

.nav li a {
  text-decoration: none;
  font-size: 28px;
  color: #f3b238;
  display: inline-block;
  width: 100%;
  position: relative;
}

.nav li a:hover {
  color: #fff;
}

.nav li a::after {
  content: "";
  width: 0%;
  height: 4px;
  background-color: #fff;
  position: absolute;
  left: 0px;
  bottom: -5px;
  border-radius: 5px;
  transition: all 0.7s ease;
}

.nav li a:hover::after {
  width: 100%;
}

/* 通用子菜单样式 */
.nav .has-submenu {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}
.nav .submenu {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.7s ease;
  padding-left: 16px;
}
.nav .submenu.active {
  max-height: 1000px;
}
.nav .submenu-toggle {
  background: none;
  border: none;
  color: #f3b238;
  font-size: 20px;
  cursor: pointer;
  transition: transform 0.3s ease;
}
.nav .submenu-toggle.expanded {
  transform: rotate(180deg);
}

@media (max-width: 769px) {
  .nav {
    position: fixed;
    inset: 0;
    background: linear-gradient(to top, #9472ff 2%, #3d00ff 98%) center/100%;
    flex-direction: column;
    align-items: center;
    padding-top: 70px;
    transform: translateX(100%);
    transition: all 0.7s ease;
  }

  .nav[data-visible=true] {
    transform: translateX(0%);
  }

  .nav-menu-button {
    position: absolute;
    display: flex;
    z-index: 10;
    justify-content: center;
    align-items: center;
    height: 80px;
    width: 80px;
    right: -10px;
    top: -10px;
    cursor: pointer;
    transition: all 0.7s ease-in-out;
  }

  .nav-menu-line {
    width: 50px;
    height: 6px;
    background-color: #d0fd66;
    border-radius: 5px;
    transition: all 0.7s ease-in-out;
  }

  .nav-menu-line::before,
  .nav-menu-line::after {
    content: "";
    position: absolute;
    width: 50px;
    height: 6px;
    background-color: #d0fd66;
    border-radius: 5px;
    transition: all 0.7s ease-in-out;
  }

  .nav-menu-line::before {
    transform: translateY(-16px);
  }

  .nav-menu-line::after {
    transform: translateY(16px);
  }

  .nav-menu-button.open .nav-menu-line {
    transform: translateX(-50px);
    background: transparent;
  }

  .nav-menu-button.open .nav-menu-line::before {
    transform: rotate(45deg) translate(35px, -35px);
  }

  .nav-menu-button.open .nav-menu-line::after {
    transform: rotate(-45deg) translate(35px, 35px);
  }

  /* 移动端子菜单适配 */
  .nav ul {
    display: flex;
    flex-direction: column;
    gap: 16px;
  }
  .nav .submenu {
    padding-top: 8px;
    padding-left: 32px;
  }
}

JavaScript 逻辑 #

const MenuButton = document.querySelector(".nav-menu-button");
const Navigation = document.querySelector(".nav");
let MenuOpen = false;

// 主菜单切换
MenuButton.addEventListener("click", () => {
  MenuOpen = !MenuOpen;
  MenuButton.classList.toggle("open", MenuOpen);
  Navigation.setAttribute("data-visible", MenuOpen.toString());
});

// 子菜单切换（事件委托支持任意层级）
document.addEventListener('click', (e) => {
  if (e.target.classList.contains('submenu-toggle')) {
    const toggleBtn = e.target;
    const submenu = toggleBtn.nextElementSibling;
    const isExpanded = toggleBtn.getAttribute('aria-expanded') === 'true';
    
    toggleBtn.setAttribute('aria-expanded', !isExpanded);
    toggleBtn.classList.toggle('expanded');
    submenu.classList.toggle('active');
  }
});

关键特性说明 #

• 任意层级嵌套：通过<ul class="submenu">嵌套在<li class="has-submenu">内，新手可直接复制该结构添加多层子菜单，无需修改CSS。
• 平滑展开动画：利用max-height过渡实现子菜单的平滑展开/收起，替代无法动画的display: none。
• 事件委托：通过监听全局点击事件处理所有子菜单按钮，避免为每个按钮单独绑定事件，提升性能。
• 可访问性优化：使用<button>作为子菜单触发器，添加aria-expanded属性标识展开状态。

内容的提问来源于stack exchange，提问作者Reza Jaferi