console 命令行工具 X clear

console

function changeColSpan()
  {
  document.getElementById("td1").colSpan="2";
  }

<table border="1"> 
  <tbody>
   <tr> 
    <th>名</th> 
    <th>姓</th> 
   </tr> 
   <tr> 
    <td id="td1">John</td> 
    <td id="td2">Adams</td> 
   </tr> 
  </tbody>
 </table> 
 <br> 
 <input type="button" onclick="changeColSpan()" value="改变 colspan">