js 前台找控件(table里找控件)

<table>
        <tr>
              <td>
                  <input type="button" value="确定" onclick="getval()">
               </td>
               <td>
                      <input type="text">
                </td>
           </tr>
</table>
点击确定按钮的找到textbox控件.

function getval()
{
    event.srcElement.parentElement.parentElement.cells[1].firstChild.value="123";
    //找textbox并给textbox赋值
}