加 media queries 实现它
media queries
@media (min-width: 434px) { .navbar-collapse{ background-color: red; } } @media (min-width: 768px) { .navbar-collapse{ background-color: unset; } }
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css"> <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/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-md navbar-light bg-light"> <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavAltMarkup" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation"> <span class="navbar-toggler-icon"></span> </button> <div class="collapse navbar-collapse" id="navbarNavAltMarkup"> <div class="navbar-nav w-75 m-auto justify-content-around"> <a class="nav-item nav-link active" href="#">Over ons <span class="sr-only">(current)</span></a> <a class="nav-item nav-link" href="#">Assortiment</a> <a class="nav-item nav-link" href="#">Specialiteiten</a> <a class="nav-item nav-link" href="#">Contact</a> </div> </div> </nav>
使用与。对应的媒体查询 navbar-expand-md 断点...
navbar-expand-md
@media(max-width: 768px) { .navbar.bg-light { background-color: red !important; } }
https://www.codeply.com/go/Fzyc7GE495
这将改变整个导航栏的颜色,而不仅仅是折叠部分。请注意,您需要使用 !important 因为你正在使用 bg-light 。默认情况下,Navbar没有颜色,因此您无需使用 bg-light 除非您需要Navbar在更大的屏幕宽度上使用颜色。
!important
bg-light