我已经编写了以下代码，但我无法获得切换导航栏。当我点击按钮时，它不会塌陷。我不知道为什么它不起作用。这可能是我的浏览器出错。但我不这么认为。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<link
rel="stylesheet"
href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css"
integrity="sha384-9aIt2nRpC12Uk9gS9baDl411NQApFmC26EwAOH8WgZl5MYYxFfc+NcPb1dKGj7Sk"
crossorigin="anonymous"
/>
<title>Bootstrap</title>
</head>
<body>
<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
<a class="navbar-brand" href="#">tindog</a>
<button
class="navbar-toggler"
type="button"
data-toggle="collapse"
data-target="#navbarTogglerDemo01"
aria-controls="navbarTogglerDemo01"
aria-expanded="false"
aria-label="Toggle navigation"
>
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarTogglerDemo01">
<ul class="navbar-nav ml-auto">
<li class="nav-item">
<a href="" class="nav-link">Contact</a>
</li>
<li class="nav-item">
<a href="" class="nav-link">Pricing</a>
</li>
<li class="nav-item">
<a href="" class="nav-link">Download</a>
</li>
</ul>
</div>
</nav>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.min.js"
integrity="sha384-OgVRvuATP1z7JjHLkuOU7Xw704+h835Lr+6QL9UvYjZE3Ipu6Tp75j7Bh/kR0JKI"
crossorigin="anonymous"></script>
</body>
</html>试试这个：
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.min.js"></script>
</head>
<body>
<nav class="navbar navbar-expand-md bg-dark navbar-dark">
<a class="navbar-brand" href="#">TinDog</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#collapsibleNavbar">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="collapsibleNavbar">
<ul class="navbar-nav">
<li class="nav-item">
<a class="nav-link" href="#">Contact</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Pricing</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Download</a>
</li>
</ul>
</div>
</nav>
<br>
<div class="container">
<h3>Hello World</h3>
</div>
</body>
</html>如果你没有正确提及脚本的顺序，你的导航栏将无法工作。
正如控制台错误中所述，Bootstrap的JavaScript需要jQuery。
因此，将其包含在head中，它将正常工作
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>