<tr id='new_tr'>
    <td id="td_1">td1</td>
    <td id="td_2">td2</td>
    <td id="td_3">td3</td>
    <td><button class="update_data" onclick="update_function(this)">修改数据</button></td>
</tr>

<script>
    function update_function(e) {
获取new_td

　　var user_id = $(e).parent().parent().attr("id")

获取td2
        var name = $(e).parent().parent().children("#td_2")[0].innerText

</script>