Bootstrap hamburger按钮点击无响应，求原因排查

你的问题根源是缺少Bootstrap交互组件依赖的JavaScript文件。Bootstrap 4的折叠菜单功能需要依赖jQuery和Popper.js，最后还得加载Bootstrap自身的JS文件——只引入CSS是没法实现按钮点击展开/收起的交互效果的。

你需要在页面的</body>标签前添加以下三个脚本：

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

完整可运行的页面结构示例：

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>导航栏示例</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
</head>
<body>
    <nav class="navbar navbar-expand-lg navbar-light bg-light">
        <a class="navbar-brand" href="#">Navbar</a>
        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarTogglerDemo02" aria-controls="navbarTogglerDemo02" aria-expanded="false" aria-label="切换导航">
            <span class="navbar-toggler-icon"></span>
        </button>

        <div class="collapse navbar-collapse" id="navbarTogglerDemo02">
            <ul class="navbar-nav mr-auto mt-2 mt-lg-0">
                <li class="nav-item active">
                    <a class="nav-link" href="#">首页 <span class="sr-only">(当前)</span></a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="#">链接</a>
                </li>
                <li class="nav-item">
                    <a class="nav-link disabled" href="#">禁用</a>
                </li>
            </ul>
            <form class="form-inline my-2 my-lg-0">
                <input class="form-control mr-sm-2" type="search" placeholder="搜索">
                <button class="btn btn-outline-success my-2 my-sm-0" type="submit">搜索</button>
            </form>
        </div>
    </nav>

    <!-- 必须添加的JS文件 -->
    <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
</html>

注意：

• 脚本加载顺序不能乱：先jQuery，再Popper.js，最后Bootstrap JS，顺序错了会导致依赖报错。
• 把脚本放在页面底部能避免阻塞页面渲染，提升加载速度。

内容的提问来源于stack exchange，提问作者marco