I manage to get it works by pressing a button and a value will load into a textbox. Here is my code

1. <asp:TextBox ID="txtResult" runat="server"></asp:TextBox><br />       
2. <input id="btn7" type="button" value="7" onclick="PassInput()" />

and my function is 

2.  function PassInput() {
3. 
   
4.       $.ajax({
5.          type: "POST",
6.          url: "VB.aspx/GetInput",
7.          data: '{name: "' + $("#btn7")[0].value + '" }',
8.          contentType: "application/json; charset=utf-8",
9.          dataType: "json",
10.          success: OnSuccess,
11. 
    
12.          failure: function (response) {
13.             alert(response.d);
14.          }
15.       });           
16.    }
18.    function OnSuccess(response) {
19.       $("#txtResult").val(response.d);
20.    }
21.    function showOutput(data) {
22.       $("#txtResult").val($("data").val());
23.    }

But, I do not want to hard code it because I have 10 button , each with different value. How do I pass the ID at  PassInput function and amend line below?

1.          data: '{name: "' + $("#btn7")[0].value + '" }',

Thanks.