Bootstrap下划线导航链接

Question

 <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous"> <nav class="navbar navbar-default"> <div class="container-fluid"> <div class="navbar-header"> <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false"> <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="#">Brand</a> </div> <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1"> <!--<ul class="nav navbar-nav"> <li class="active"><a href="#">Link <span class="sr-only">(current)</span></a></li> <li><a href="#">Link</a></li> </ul>--> <ul class="nav navbar-nav navbar-right"> <li class="active"><a href="#">Link <span class="sr-only">(current)</span></a></li> <li><a href="#">Link</a></li> <li><a href="#">Link</a></li> </ul> </div> </div> </nav> 

我在这段代码中遇到了麻烦：

.navbar-default .navbar-nav > .active > a:after {
   content: "";
   position: absolute;
   width: 100%;
   height: 3px;
   bottom: 0;
   left: 0;
   background-color: #1B94E1;

    -webkit-transform: scaleX(0);
            transform: scaleX(0);
   -webkit-transition: all 0.3s ease-in-out 0s;
           transition: all 0.3s ease-in-out 0s;
}

本质上，我想使用CSS ::after伪类创建各种下划线。 但是，似乎什么都没有发生。 请注意，我正在使用Bootstrap并将这些样式应用于导航栏。 谢谢！

这是一个codepen： http ://codepen.io/Hudson_Taylor11/pen/ZBGGXQ

Answer 1

注释掉您的过渡即可解决。

.navbar-default .navbar-nav > .active > a:after {
   content: "";
   position: absolute;
   width: 100%;
   height: 3px;
   bottom: 0;
   left: 0;
   background-color: #1B94E1;

  /*  -webkit-transform: scaleX(0);
            transform: scaleX(0);
    -webkit-transition: all 0.3s ease-in-out 0s;
           transition: all 0.3s ease-in-out 0s;
  */
}

http://codepen.io/0rfila/pen/rWVVqj

这是一些有关动画伪动画的更多信息： https ://cssanimation.rocks/pseudo-elements/

Answer 2

这是工作码本

.navbar-default .navbar-nav a { border-bottom: 2px solid red; padding: 0px; margin: 15px; }

http://codepen.io/SESN/pen/QGbbmL