导航栏在移动端视图自动展开问题求助

问题根源 #

你的代码里，移动端视图下#nav_bar未设置初始高度为0%，默认会根据内容撑开高度，导致页面加载或窗口调整到移动端尺寸时导航栏自动展开；同时移动端下按钮的初始显示状态也不符合预期。

修复步骤 #

1. 设置导航栏初始隐藏状态：在移动端媒体查询中给#nav_bar添加height: 0%，确保默认隐藏
2. 修正按钮初始显示状态：移动端下默认显示open-btn，隐藏close-btn
3. 同步aria-expanded属性（可选但推荐）：在openNav和closeNav函数里更新按钮的aria-expanded值，提升页面可访问性

修改后的完整代码 #

JavaScript #

function closeNav() {
  const navBar = document.getElementById("nav_bar");
  const openBtn = document.getElementById("open-btn");
  const closeBtn = document.getElementById("close-btn");
  
  navBar.style.height = "0%";
  openBtn.style.display = "inline-block";
  closeBtn.style.display = "none";
  // 更新aria-expanded状态
  openBtn.setAttribute("aria-expanded", "false");
  closeBtn.querySelector("i").setAttribute("aria-expanded", "false");
}

function openNav() {
  const navBar = document.getElementById("nav_bar");
  const openBtn = document.getElementById("open-btn");
  const closeBtn = document.getElementById("close-btn");
  
  navBar.style.height = "100%";
  openBtn.style.display = "none";
  closeBtn.style.display = "inline-block";
  // 更新aria-expanded状态
  openBtn.setAttribute("aria-expanded", "true");
  closeBtn.querySelector("i").setAttribute("aria-expanded", "true");
}

CSS #

body {
  background: url(images/bg-img-01.jpg) no-repeat;
  background-size: cover;
}

*,
*::after,
*::before {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

#nav_bar {
  background: radial-gradient( ellipse at top, rgba(196, 199, 200, 0.8), rgba(250, 255, 255, 0.02) 60%, rgba(0, 0, 0, 0) 1%);
  position: fixed;
  top: 0;
  width: 100%;
}

#nav_bar>img {
  display: none;
}

.nav {
  background: none;
  overflow: hidden;
  display: flex;
  margin-inline: auto;
  flex-direction: row;
  justify-content: space-around;
  align-items: center;
  list-style: none;
  width: 65%;
  left: 20%;
  padding: 1.4em;
}

.list-item {
  text-decoration: none;
  color: #CBD5DF;
  font-weight: bolder;
}

.list-item {
  position: relative;
}

.list-item::before {
  position: absolute;
  content: "";
  background-color: #535792;
  height: 4px;
  width: 0%;
  top: 25px;
  transition: all .3s ease-in;
}

.list-item:hover::before {
  width: 100%;
}

.list-item:hover {
  color: #C4C7C8;
}

#close-btn,
#open-btn {
  display: none;
}

@media only screen and (max-width:768px) {
  #nav_bar>img {
    display: block;
    position: absolute;
    width: 10em;
    left: 20%;
    top: 10%;
  }
  #nav_bar {
    width: 100%;
    position: fixed;
    z-index: 1;
    top: 0;
    overflow: hidden;
    transition: 0.5s;
    height: 0%; /* 添加这行，默认隐藏导航栏 */
  }
  .nav {
    position: relative;
    display: flex;
    flex-direction: column;
    gap: 1.2rem;
    top: 20%;
    width: 100%;
    text-align: center;
    margin-top: 30px;
  }
  .list-item {
    text-decoration: none;
    display: block;
    color: #ffdada;
    font-size: 1.5rem;
    transition: 0.3s;
  }
  #close-btn {
    display: none; /* 移动端默认隐藏关闭按钮 */
    position: absolute;
    right: 25px;
    top: 20px;
    font-size: 2rem;
    color: #818181;
    transition: all 0.3s;
  }
  #open-btn {
    display: block; /* 移动端默认显示打开按钮 */
    position: absolute;
    right: 25px;
    top: 20px;
    font-size: 2rem;
    color: #818181;
    transition: all 0.3s;
  }
  #close-btn:hover {
    color: #fff;
  }
}

HTML #

<body>
  <div id="nav_bar">
    <a href="#" id="close-btn">
      <i aria-expanded="false" onclick="closeNav()" class="bi bi-x-lg"></i>
    </a>
    <img src="assests/images/moon.png" alt="" />

    <div class="nav">
      <a class="list-item" href="#">Home</a>
      <a class="list-item" href="#">About Me</a>
      <a class="list-item" href="#">Projects</a>
      <a class="list-item" href="#">C.V</a>
      <a class="list-item" href="#">Contact</a>
    </div>
  </div>
  <a aria-expanded="false" href="#" id="open-btn" onclick="openNav()"><i class="bi bi-list"></i></a>
  <script src="assests/nav.js"></script>
</body>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js" integrity="sha384-MrcW6ZMFYlzcLA8Nl+NtUVF0sA7MsXsP1UyJoMp4YLEuNSfAP+JcXn/tWtIaxVXM" crossorigin="anonymous"></script>

内容的提问来源于stack exchange，提问作者Usama Khan