HTML和Javascript中的排序表-第一列问题

<table id="myTable">
  <tr>
    <th onclick="sortTable(0)">第一列</th>
    <th>其他列</th>
  </tr>
  <tr>
    <td>3</td>
    <td>其他数据</td>
  </tr>
  <tr>
    <td>1</td>
    <td>其他数据</td>
  </tr>
  <tr>
    <td>2</td>
    <td>其他数据</td>
  </tr>
</table>

function sortTable(columnIndex) {
  var table, rows, switching, i, x, y, shouldSwitch;
  table = document.getElementById("myTable");
  switching = true;
  while (switching) {
    switching = false;
    rows = table.rows;
    for (i = 1; i < (rows.length - 1); i++) {
      shouldSwitch = false;
      x = rows[i].getElementsByTagName("td")[columnIndex];
      y = rows[i + 1].getElementsByTagName("td")[columnIndex];
      if (Number(x.innerHTML) > Number(y.innerHTML)) {
        shouldSwitch = true;
        break;
      }
    }
    if (shouldSwitch) {
      rows[i].parentNode.insertBefore(rows[i + 1], rows[i]);
      switching = true;
    }
  }
}