jQuery 获取遍历获取table中每一个tr中的第一个td

<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>