下面的例子更改了表元横跨的列数 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>蜜蜂教程(mifengjc.com)</title>
  <script>
    function displayResult() {
      document.getElementById("myHeader1").colSpan = "2";
    }
  </script>
</head>
<body>

  <table border="1">
    <tr>
      <th id="myHeader1">月份</th>
      <th id="myHeader2">存款</th>
    </tr>
    <tr>
      <td>January</td>
      <td>$100.00</td>
    </tr>
    <tr>
      <td>February</td>
      <td>$10.00</td>
    </tr>
    <tr>
      <td>March</td>
      <td>$80.00</td>
    </tr>
  </table>
  <br>
  <button type="button" onclick="displayResult()">改变第一个单元格的横跨列数</button>

</body>
</html>
        