Read and Update TextBox value in GridView on Row Button Click using jQuery in ASP.Net

How to Read and Update Textbox value in Gridview on Row Button Click Using Jquery

There is a Gridview with textbox and button in each row. I am getting the value of textbox and another column. After that I am creating SHA512 of both values then again its need to update to the same password textbox on button clicked for that corresponding row.

How should I do this?

Below is the JQuery event I am using: 

        <script type="text/javascript">
            $(function () {
                $("[id*=grduserdetail]").find("[id*=btnpass]").click(function () {
                    //Reference the GridView Row.
                    var row = $(this).closest("tr");
                    var unm = row.find('.userid').text();
                    var pwd = row.find($('[id*=txtpass]')).val();
                    var pwdLength = false;
                    if (pwd.length >= 6)
                        pwdLength = true;

                    var hasUpperCase = /[A-Z]/.test(pwd);
                    var hasLowerCase = /[a-z]/.test(pwd);
                    var hasNumbers = /\d/.test(pwd);
                    var hasNonalphas = /[@#&!$%^&*()]/.test(pwd);

                    if (!((hasUpperCase + hasLowerCase + hasNumbers + hasNonalphas + pwdLength) > 4)) {
                        alert('Password must be 6 charaters long and contain one Upper case one lower case one digit and one special character !');
                        return false;
                    } else {

                        //$(this).prev()[0].value = SHA512(unm.text() + pwd.val());
                        pwd.value = SHA512(unm + pwd);
                        //document.getElementById("shhidden").value = SHA512(unm + pwd);
                        return true;
                    }

                });
            });
        </script>

<asp:GridView ID="grduserdetail" runat="server" CssClass="gridfont" Width="100%" AutoGenerateColumns="False" CellPadding="4" DataKeyNames="user_id" Height="21px">
    <HeaderStyle VerticalAlign="Top" CssClass="gridfontmaroon" />
    <RowStyle CssClass="gridfont" />
    <Columns>
        <asp:TemplateField HeaderText="S.No">
            <ItemTemplate>
                <%# Container.DataItemIndex + 1 %>
            </ItemTemplate>
            <HeaderStyle HorizontalAlign="Center" />
        </asp:TemplateField>
        <asp:TemplateField HeaderText="User Id">
            <ItemTemplate>
                <asp:Label ID="lblid" runat="server" Text='<%#Server.HtmlEncode(Eval("user_id").ToString()) %>' CssClass="userid"> </asp:Label>
            </ItemTemplate>
            <HeaderStyle HorizontalAlign="Center" />
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Change Password" HeaderStyle-Width="250px">
            <ItemTemplate>
                <asp:TextBox ID="txtpass" MaxLength="20" runat="server" Font-Size="0.8em" autocomplete="off" TextMode="Password" Style="left: 3px; position: relative; top: 0px"
                    Width="120px" AutoCompleteType="None" autofill="false"></asp:TextBox>

                <asp:Button ID="btnpass" runat="server" Text="Change Password" CommandName="Reset" Width="120px" OnClick="btnpass_Click" OnClientClick="return validatePassword(this);" />

            </ItemTemplate>

            <ItemStyle VerticalAlign="Top" HorizontalAlign="Left" />
            <HeaderStyle HorizontalAlign="Center" Width="25%" />

        </asp:TemplateField>
        <%--<asp:ButtonField CommandName="Reset" Text="Change Password" ButtonType="Button" CausesValidation="false" ValidationGroup="1" />--%>
    </Columns>
</asp:GridView>