css--关于visibility设置 “collapse”值问题

<table cellspacing="0" class="table">
  <tbody><tr>
    <th>Fruits</th>
    <th>Vegetables</th>
    <th>Rocks</th>
  </tr>
  <tr>
    <td>Apple</td>
    <td>Celery</td>
    <td>Granite</td>
  </tr>
  <tr>
    <td>Orange</td>
    <td>Cabbage</td>
    <td>Flint</td>
  </tr>
</tbody></table>

var btns = document.getElementsByTagName('button'),
    rows = document.getElementsByTagName('tr');
 
btns[0].addEventListener('click', function () {
  rows[1].className = '<a href="http://www.php1.cn/">vc</a>';
}, false);
 
btns[1].addEventListener('click', function () {
  rows[1].className = 'vh';
}, false);
 
btns[2].addEventListener('click', function () {
  rows[1].className = '';
}, false);

body {
  text-align: center;
  padding-top: 20px;
  font-family: Arial, sans-serif;
}
 
table {
  border-collapse: separate;
  border-spacing: 5px;
  border: solid 1px black;
  width: 500px;
  margin: 0 auto;
}
 
th, td {
  text-align: center;
  border: solid 1px black;
  padding: 10px;
}
 
.vc {
  visibility: collapse;
}
 
.vh {
  visibility: hidden;
}
 
button {
  margin-top: 5px;
}