Javascript works only first textbox inside gridview

Question

User1052662409 posted

Hello All,

I have a gridview. This gridview have a textbox in template field.

  <asp:TemplateField HeaderStyle-CssClass="thead-dark" HeaderText="Request No.">
                                                    <ItemTemplate>

 
                                                         <asp:TextBox runat="server" ID="txtfinAmt" CssClass="textboxsize req" onkeypress="ValidateMemComment(event);" onchange="CheckAvailability()"> </asp:TextBox>
                                                    </ItemTemplate>
                                                </asp:TemplateField>

Below is my java script function which I am calling on "onchange" event of textbox.

 <script type="text/javascript">  
        function CheckAvailability() {
            var req_no =  $('[id$=txtfinAmt]').val();
            alert(req_no);
            $.ajax({
                type: "POST",
                url: "Topic.asmx/CheckReqNumber", // this for calling the web method function in cs code.  
                data: '{req_no: "' + req_no    + '" }',// user name or email value  
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: OnSuccess,
                failure: function (response) {
                    alert(response);
                }
            });   
        }
        function OnSuccess(response) {
            switch (response.d) {
                case "true":
                    alert("Req. No already exists");
                    $('[id$=txtfinAmt]').val("");
                    $('[id$=txtfinAmt]').focus();
                    break;
                case "false":
                    //msg.style.display = "block";
                    //msg.style.color = "green";
                    //msg.innerHTML = "User Name Or Email Available";
                    break;
            }
        }   

    </script> 

The problem is that, this CheckAvailability() funxtion works only for first textbox of gridview. when I try to run this function by putting some value in another textbox then it shows the textbox value is empty

Please suggest.