twitter-bootstrap:当鼠标悬停在<a> -tag中的btn-group时,如何摆脱带下划线的按​​钮文字？

.btn-group a {
  text-decoration: none;
}

document.querySelectorAll('.btn-group a').forEach(function(link) {
  link.classList.add('btn');
});

<div class="btn-group" role="group" aria-label="Basic example">
 <button type="button" class="btn btn-secondary">Left</button>
 <button type="button" class="btn btn-secondary">Middle</button>
 <button type="button" class="btn btn-secondary">Right</button>
</div>