<div class="container">
  <ul>
    <li><a href="#">Uno Uno Uno</a></li>
    <li><a href="#">Dos</a></li>
    <li><a href="#">Tres</a></li>
    <li><a href="#">Quatro</a></li>
  </ul>
  <hr />
</div>
* {
  box-sizing: border-box;
}

body {
  font: 300 100% 'Helvetica Neue', Helvetica, Arial;
}

.container {
  width: 50%;
  margin: 0 auto;
}

ul {
  display: flex;
  width: 100%;
  justify-content: space-around;
}

ul li {
  text-align: center;
  list-style: none;
}

a {
  display: block;
  width: 10%0;
  padding: .75rem 0;
  margin: 0;
  text-decoration: none;
  color: #333;
}

hr {
  height: .25rem;
  margin: 0;
  width: 0;
  background: tomato;
  border: none;
  transition: all 250ms;
}
jQuery(document).ready(function($) {  
  $('ul li').hover(function() {
   var left = $(this).offset().left - $('ul').offset().left,
       width = $(this).width();
   $('hr').css({
     'margin-left': left,
     'width'      : width
   })
  }).first().mouseenter().mouseleave()
});

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.0/jquery.min.js