如何为适配移动端的Navbar创建可用的下拉菜单

问题背景 #

现有基于HTML/CSS/JS的移动端Navbar，汉堡菜单点击带动画效果，需为「Products」导航项添加适配移动端的下拉菜单。

修改后的完整代码 #

HTML #

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>NavBar</title>
    <link rel="stylesheet" href="style2.css">
    <script defer src="script2.js"></script>
</head>
<body>
    <div class="root">
        <header class="header">
            <div class="navbar">
                <div class="navbar-content">
                    <a href="#" class="logo">
                        <img src="media/insert logo img here" alt="Logo" class="logo-img">
                    </a>
                    <nav class="nav">
                        <ul class="nav-list">
                            <li class="nav-item">
                                <a href="#" class="nav-link">Home</a>
                            </li>
                            <li class="nav-item dropdown">
                                <a href="#" class="nav-link dropbtn">Products</a>
                                <div class="dropdown-content">
                                    <a href="#" class="nav-link">Dropdown one</a>
                                    <a href="#" class="nav-link">Dropdown two</a>
                                </div>
                            </li>
                            <li class="nav-item">
                                <a href="#" class="nav-link">About</a>
                            </li>
                            <li class="nav-item">
                                <a href="#" class="nav-link">Contact</a>
                            </li>
                        </ul>
                    </nav>
                    <div class="hamburger">
                        <div class="bar"></div>
                        <div class="bar"></div>
                        <div class="bar"></div>
                    </div>
                </div>
            </div>
        </header>
    </div>
</body>
</html>

CSS #

/* RESET */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

ul {
    list-style: none;
}

a {
    text-decoration: none;
    color: inherit;
}
/* BASE STYLE */
body {
    background-color: #e8f0f7;
    font-family: 'Inter', sans-serif;
    min-height: 500vh;
}


/* NORMAL STYLES */
.header {
    position: fixed;
    width: 100%;
}

.navbar {
    background-color: rgb(19, 22, 26);
}

.navbar-content {
    min-height: 60px;
    max-width: 1200px;
    padding: 0 30px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    vertical-align: middle;
    display: flex;
    column-gap: 10px;
    align-items: center;
}

.logo-img {
    height: 30px;
}

.logo-text {
    font-size: 20px;
    color: #fff;
    font-weight: 500;
    letter-spacing: -0.5px;
}
.nav {
    transition: all 0.3s ease-in-out;
}

.nav-list {
    display: flex;
    column-gap: 40px;
}

.nav-link{
    color: rgba(255, 255, 255, 0.75);
    transition: all 0.2s;
}

.nav-link:hover, .nav-link:focus {
    color: rgba(255, 255, 255, 1);
}

.hamburger {
    cursor: pointer;
    display: none;
}

.bar {
    height: 2px;
    width: 27px;
    background-color: #fff;
    margin: 5px 0;
    opacity: 0.8;
    transition: all 0.3s ease-in-out;
}

/* 下拉菜单基础样式 */
.dropdown {
    position: relative;
}

.dropdown-content {
    display: none;
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    background-color: rgb(19, 22, 26);
    border-radius: 4px;
    padding: 10px 0;
    min-width: 150px;
    text-align: center;
}

/* 桌面端hover显示下拉 */
.dropdown:hover .dropdown-content {
    display: block;
}

/* For JS */
.nav-open {
    left: 50% !important;
}

.hamburger-open .bar:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}

.hamburger-open .bar:nth-child(2) {
    transform: translateY(7px) rotate(45deg);
    opacity: 0;
}

.hamburger-open .bar:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* 移动端下拉菜单激活样式 */
.dropdown-active .dropdown-content {
    display: block;
}

/* MEDIA QUERIES */
@media (max-width: 650px) {
    .nav {
        position: fixed;
        top: 60px;
        left: -100%;
        transform: translateX(-50%);
        background-color: rgb(19, 22, 26);
        width: 100%;
        padding: 10px 0 25px;
    }

    .nav-list {
        flex-direction: column;
        align-items: center;
        row-gap: 20px;
    }

    .nav-link {
        font-size: 14px;
    }
    
    .hamburger {
        display: block;
    }

    /* 移动端下拉菜单调整 */
    .dropdown-content {
        position: static;
        transform: none;
        margin-top: 15px;
        padding-top: 15px;
        border-top: 1px solid rgba(255,255,255,0.1);
        row-gap: 10px;
        display: flex;
        flex-direction: column;
    }
}

@media (max-width: 360px) {
    .top-bar__content {
        font-size: 10px;
    }
}

JavaScript #

const navEl = document.querySelector('.nav');
const hamburgerEl = document.querySelector('.hamburger');
const navItemsEls = document.querySelectorAll('.nav-item');
const dropdownEl = document.querySelector('.dropdown');

hamburgerEl.addEventListener('click', () => {
    navEl.classList.toggle('nav-open');
    hamburgerEl.classList.toggle('hamburger-open');
});

navItemsEls.forEach(navItemEl => {
    navItemEl.addEventListener('click', (e) => {
        // 普通导航项点击关闭导航栏，下拉项仅切换菜单状态
        if (!navItemEl.classList.contains('dropdown')) {
            navEl.classList.remove('nav-open');
            hamburgerEl.classList.remove('hamburger-open');
        } else {
            e.stopPropagation();
            dropdownEl.classList.toggle('dropdown-active');
        }
    });
});

// 点击页面其他区域关闭导航栏和下拉菜单
document.addEventListener('click', (e) => {
    if (!navEl.contains(e.target) && !hamburgerEl.contains(e.target)) {
        navEl.classList.remove('nav-open');
        hamburgerEl.classList.remove('hamburger-open');
        dropdownEl.classList.remove('dropdown-active');
    }
});

关键修改说明 #

• HTML修正：修复「Contact」项的类名错误（nav-tem改为nav-item），确保选择器正常生效
• CSS新增：
  • 桌面端hover触发下拉的基础样式
  • 移动端下拉菜单改为静态布局，添加分隔线增强视觉层级
  • 新增dropdown-active类控制移动端下拉菜单的显示/隐藏
• JS逻辑优化：
  • 区分普通导航项和下拉项的点击行为，避免下拉菜单触发导航栏关闭
  • 点击页面空白区域时，同步关闭导航栏和下拉菜单
  • 阻止下拉项点击事件冒泡，保证交互逻辑独立

内容的提问来源于stack exchange，提问作者Ackersand