我正在尝试使用在特定视口(viewport)宽度折叠的 Bootstrap 创建导航栏。现在，我想看到的是，如果导航栏折叠，navbar-brand 就会消失，并且当前事件的导航项(例如“主页”、“关于”等)将在离开，从而使访问者能够看到他们所在的页面。
我是一个完全的 bootstrap 菜鸟，我有点希望看到在导航栏折叠/展开时添加一个 css 类，但它不能那样工作。
<html lang="en"><head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
</head>
<body>
<nav class="navbar navbar-inverse navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#">Project name</a>
</div>
<div id="navbar" class="collapse navbar-collapse">
<ul class="nav navbar-nav">
<li class="active"><a href="#">Home</a></li>
<li><a href="#about">About</a></li>
<li><a href="#contact">Contact</a></li>
</ul>
</div><!--/.nav-collapse -->
</div>
</nav>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="../../assets/js/vendor/jquery.min.js"><\/script>')</script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
</body></html>最佳答案
不完全是“开箱即用”，但是一些 CSS 可以与 Bootstrap 4 一起使用(没有 jquery 或 dup 标记)...
https://www.codeply.com/go/5T4icATKjl
这会覆盖导航栏折叠行为以使用 visibility 而不是 display。这样我们就可以控制 active 导航项的显示。
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" ></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<style>
.navbar .collapse {
visibility: hidden;
display: block;
}
.navbar .collapse.show {
visibility: visible;
}
@media (max-width: 767px) {
.navbar-nav .nav-link.active {
visibility: visible;
}
.collapsing {
transition: all 0.35s ease;
height: 40px !important;
}
.collapse:not(.show) .navbar-nav .nav-item:not(.active) {
display: none;
}
}
@media (min-width: 768px) {
.navbar .collapse .navbar-nav .nav-item {
visibility: visible;
}
}
</style>
<body>
<nav class="navbar navbar-expand-md fixed-top navbar-dark bg-dark">
<div class="container">
<div class="collapse" id="navbar1">
<div class="navbar-nav flex-md-row">
<a class="nav-item navbar-brand" href="#">Project name</a>
<a class="nav-item nav-link" href="#">Home</a>
<a class="nav-item nav-link" href="#">About</a>
<a class="nav-item nav-link active" href="#">Contact</a>
</div>
</div>
<button class="navbar-toggler align-self-start" type="button" data-toggle="collapse" data-target="#navbar1">
<span class="navbar-toggler-icon"></span>
</button>
</div>
</nav>
</body>请注意@media 查询与 768px 的 navbar-expand-md 断点一起进行。如果需要，您可以更改它以使用不同的断点。
navbar-expand-sm - 576px
navbar-expand-lg - 992px
navbar-expand-xl - 1200px
还有另一种使用重复导航栏导航链接的解决方案，但这需要额外的标记，我认为上面的纯 CSS 解决方案更清晰。
关于javascript - Bootstrap 4 : Show active nav-item on Navbar collapse，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/49464453/