CSS - a

a {
  position: relative;
  white-space: normal;
  border-bottom: .0625rem dashed #1abc9c;
  text-decoration: none;
  color: #1abc9c;
}
a:after {
  position: absolute;
  bottom: -.0625rem;
  left: 100%;
  width: 0;
  border-bottom: .0625rem solid #1abc9c;
  content: "";
  transition: width .35s,left .35s
}
a:hover:after {
  left: 0;
  width: 100%;
  transition: width .35s
}

参考自 Hran