js复制一行，并将序列数字加一,目前总是将第一行数值加一

Question

 # <table class="tablelist">
        <thead>
            <tr>
                <th style="text-align: center"><input type="checkbox" id="allcbx" /></th>
                <th>等级</th>
                <th>工资</th>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td style="text-align: center">
                    <input type="checkbox" name="ids" value="" disabled="disabled" />
                </td>
                <td><input type="text" readonly="readonly" style="border:0px;" value="1" class="grade" name="grade" id="grade" /></td>
                <td><input class="text5" type="text" name="average" /></td>
            </tr>
        </tbody>
    </table>
    <div class="operate3">
        <span class="add">+ 增加等级</span> |
        <span class="del">- 删除选中等级</span>
    </div>
        <script>
    $(function () {
        $(".add").click(function () {
            var tr = $(".tablelist tbody>tr:last-child").clone().attr("clone", true);
            tr.find("input[name='ids']").removeAttr("disabled");
            //document.getElementById('grade').value = parseInt(document.getElemeId('grade').value) + 1;
            tr.appendTo($(".tablelist tbody"));
        });

        $(".del").click(function () {
            var cbx = $("input[name='ids']:checked");

            if (cbx.length > 0) {
                cbx.parent().parent().remove();
            } else {
                exAlert('请选择至少一个记录！');
            }
        });

        $(".tablelist").on("click", ".cbx", function () {
            if ($(this).is(":checked")) {
                $(this).prev().val("true");
            } else {
                $(this).prev().val("false");
            }
        });
    });
</script>

Answer 1

        $(".add").click(function () {
            var tr = $(".tablelist tbody>tr:last-child").clone().attr("clone", true);
            tr.find("input[name='ids']").removeAttr("disabled")
            tr.find("#grade").val($('.tablelist tr').length);
            //document.getElementById('grade').value = parseInt(document.getElemeId('grade').value) + 1;
            tr.appendTo($(".tablelist tbody"));
        });