如何在引导程序 4 中为活动类导航项制作边框？答案

【问题标题】：How can i make border for active class nav-item in bootstrap 4?如何在引导程序 4 中为活动类导航项制作边框？
【发布时间】：2019-06-25 18:51:15
【问题描述】：

我想更改nav-item 中的一些样式。我制作了另一个样式表，并在其中制作了这段代码。问题是在 Internet Explorer 中它运行良好，但在 Firefox 中没有任何变化。如何在nav-link active 中进行一些更改？

例如，当导航处于活动状态时，我希望有一个边框底部。

<div class="container">
    <nav class="navbar navbar-expand-lg navbar-light py-md-5">
        <a class="navbar-brand" href="#">Navbar</a>

        <div class="justify-content-end  collapse navbar-collapse" id="navbarNavAltMarkup">
            <div class="navbar-nav">
                <a class="nav-item nav-link active" href="#">Home <span class="sr-only">(current)</span></a>
                <a class="nav-item nav-link" href="#">ABOUT US</a>
                <a class="nav-item nav-link" href="#">SERVICES</a>
                <a class="nav-item nav-link" href="#">TEAM</a>
                <a class="nav-item nav-link" href="#">CLIENTS</a>
                <a class="nav-item nav-link" href="#">CONTACT</a>
            </div>
        </div>
    </nav>
</div>

【问题讨论】：

自定义样式在哪里？

标签： css bootstrap-4

【解决方案1】：

在您的自定义样式中添加此 css

.nav-item.active
{
  border-bottom:2px solid #f00;
}

.nav-item.active
{
  border-bottom:2px solid #f00;
}

  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"></script>
  
  <nav class="navbar navbar-expand-lg navbar-light py-md-5">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#collapsibleNavbar">
    <span class="navbar-toggler-icon"></span>
  </button>
  <div class="justify-content-end  collapse navbar-collapse" id="collapsibleNavbar">
    <ul class="navbar-nav">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home </a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">ABOUT US</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">SERVICES</a>
      </li>  
       <li class="nav-item">
        <a class="nav-link" href="#">TEAM</a>
      </li>  
       <li class="nav-item">
        <a class="nav-link" href="#">CLIENTS</a>
      </li>  
       <li class="nav-item">
        <a class="nav-link" href="#">CONTACT</a>
      </li>  
    </ul>
  </div>  
</nav>

【讨论】：

【解决方案2】：

$('.nav-link').click(function() {
  $('.nav-link').removeClass("active");
  $('li.nav-item.active').removeClass("active");
  $(this).addClass("active");
});

.active {
  border-bottom: 2px solid #f00;
}

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"></script>

<nav class="navbar navbar-expand-lg navbar-light py-md-5">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#collapsibleNavbar">
    <span class="navbar-toggler-icon"></span>
  </button>
  <div class="justify-content-end  collapse navbar-collapse" id="collapsibleNavbar">
    <ul class="navbar-nav">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home </a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">ABOUT US</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">SERVICES</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">TEAM</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">CLIENTS</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">CONTACT</a>
      </li>
    </ul>
  </div>
</nav>

【讨论】：