如何使用Prototype突出显示表格行？

 <thead>
    <tr>
      <th>姓名</th>
      <th>年龄</th>
      <th>城市</th>
    </tr>
  </thead>
 <tbody>
    <tr>
      <td>张三</td>
      <td>25</td>
      <td>北京</td>
    </tr>
    <tr>
      <td>李四</td>
      <td>30</td>
      <td>上海</td>
    </tr>
    <tr>
      <td>王五</td>
      <td>28</td>
      <td>广州</td>
    </tr>
  </tbody>
</table>

table {
  border-collapse: collapse;
  width: 100%;
}

th,
td {
  border: 1px solid black;
  padding: 8px;
  text-align: left;
}

tr:hover {
  background-color: #f5f5f5;
}

document.observe('dom:loaded', function() {
  $$('#myTable tr').each(function(row) {
    row.observe('mouseover', function() {
      row.addClassName('highlight');
    });

    row.observe('mouseout', function() {
      row.removeClassName('highlight');
    });
  });
});

.highlight {
  background-color: yellow;
}