Adding TextBox Values using Javascript

The following code sample shows how to add the textbox values using javascript.

The keyup event of the textbox is used. Three textboxes is use , the functionality is to add the first and second textboxes and total in third textbox.

The Javascript Function follows :

        function KeyUpEvent()
        {
           var txt1 = document.getElementById("txt1");
           var txt2 = document.getElementById("txt2");
           var txt3 = document.getElementById("txt3");
           if ((txt1.value != "") && (txt2.value != ""))
           {
                txt3.value = parseInt(txt1.value) + parseInt(txt2.value); 
           }
        }

           
        <asp:TextBox ID="txt1" runat="server"></asp:TextBox>
        <asp:TextBox ID="txt2" runat="server"></asp:TextBox>
        <asp:TextBox ID="txt3" runat="server"></asp:TextBox>

        txt1.Attributes.Add("onKeyUp", "javascript:KeyUpEvent();");
        txt2.Attributes.Add("onKeyUp", "javascript:KeyUpEvent();");