W3School TIY
编辑您的代码：
<!DOCTYPE html> <html> <head> <style> table,th,td { border:1px solid black; } </style> </head> <body> <h3>关于如何访问 COLGROUP 元素的一个演示</h3> <table> <colgroup id="myColgroup" span="2" style="background:red"></colgroup> <tr> <th>ISBN</th> <th>Title</th> <th>Price</th> </tr> <tr> <td>3476896</td> <td>My first HTML</td> <td>$53</td> </tr> <tr> <td>5869207</td> <td>My first CSS</td> <td>$49</td> </tr> </table> <p>请点击按钮，来获得 COLGROUP 元素应该横跨的列数。</p> <p id="demo"></p> <button onclick="myFunction()">试一下</button> <script> function myFunction() { var x = document.getElementById("myColgroup").span; document.getElementById("demo").innerHTML = x; } </script> </body> </html>
查看结果: