django js 实现表格动态标序号

<table class="table table-striped">
                <thead>
                <tr class="key_words_head">
                    <th>序号</th>
                    <th>类目</th>
                    <th>关键词</th>
                    <th>操作</th>
                </tr>
                </thead>
                <tbody id="key_words_body">
                {% for keywords in classify_keywords_obj %}
                    <tr class="key_words_tbody">
                        <td id="td_num"></td>
                        <td id="hide_id">{{ keywords.id }}</td>
                        <td id="td_classify">{{ keywords.classify.classify_name }}</td>
                        <td id="td_keywords">{{ keywords.keywords }}</td>
                        <td><a href="javascript:void(0);" onclick="show_change_model('{{ keywords.id }}')">编辑</a>
                            <a href="javascript:void(0);" style="color: red" onclick="del_settings('{{ keywords.id }}',this)">删除</a></td>
                    </tr>
                {% endfor %}
                </tbody>
            </table>

    <script>
        function xu_hao() {
            var otable = $('tr.key_words_tbody').length;
            for (var i = 0; i < otable + 1; i++) {
                $('tr.key_words_tbody').eq(i).children("td#td_num").empty();
                $('tr.key_words_tbody').eq(i).children("td#td_num").append(i + 1);
            }
        }
    </script>