jQuery 获取遍历获取table中每一个tr中的第一个td的方法

<tbody id="already_question_list">   <tr>     <td><?php echo $val['unique_number']; ?></td>     <td><?php echo $val['year'].'-'.$val['series']; ?></td>     <td><?php echo $val['content'] ?></td>     <td><?php echo $val['knowledges'] ?></td>     <td><?php echo $val['last_admin']; ?></td>     <td>       <input type="button" class="btn" value="－" data-score="<?php echo $val['score']; ?>" onclick='remove_selected(this);'/>/       <input type="hidden" name="question_numbers[]" value="<?php echo $val['unique_number']; ?>"/>     </td>   </tr> </tbody>  <script>   var leng = $("#already_question_list tr").length;   var filter_numbs = new Array();   for(var i=0; i<=leng; i++)   {     numberStr = $("#already_question_list tr").eq(i).find("td:first").html();     filter_numbs.push(numberStr);   } </script>