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> 

I am having trouble with this snippet of code:

.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;
}

Essentially, I want to use the CSS ::after pseudoclass to create an underline of sorts. However, nothing seems to be happening. Note that I am using Bootstrap and applying these styles to the navbar. Thanks!

Here is a codepen: http://codepen.io/Hudson_Taylor11/pen/ZBGGXQ

Answer 1

Commenting out your transitions fixes it.

.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

Here's some more info on animating pseudos: https://cssanimation.rocks/pseudo-elements/

Answer 2

Here is the working codepen

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

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