How to Get TextBox value from GridView using JavaScript

First Design Gridview as :

<asp:GridView ID="GVReue" runat="server" ">
  <Columns>
        <asp:TemplateField HeaderText="Item Name">
    <ItemTemplate>
        <asp:Label ID="lblItemName" Text=' <%# Eval("fldItemName") %>'
           runat="server"></asp:Label>
    </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Quantity">
    <ItemTemplate>
        <asp:TextBox ID="txtQty" ToolTip=' <%# Eval("fldQuntity") %>' onblur="Calculation(this.value)"
            runat="server" />
    </ItemTemplate>
       </asp:TemplateField>
 </Columns>
        <EmptyDataTemplate>
            No Record Found....!!!
        </EmptyDataTemplate>
</asp:GridView>

Design as

 

 

Then Use Script in Head tag as

<script type="text/javascript">
    function Calculation() {
    var grid = document.getElementById("<%= GVReue.ClientID%>");
    for (var i = 0; i < grid.rows.length - 1; i++) {
    var txtAmountReceive = $("input[id*=txtQty]")
    if (txtAmountReceive[i].value != '') {
    alert(txtAmountReceive[i].value);
      }
      }
}
</script>

Then Get value of TxtQty Textbox as