Question

Looking at many forums this seems to be the solution, however, it doesn’t seem to work for me:

 function update() {

     alert("hello world");

     var test = document.getElementById("<%=InCL.ClientID%>").value;    

     alert(test);

 } 

and the asp/html is:

<asp:TextBox ID="InCL" runat="server" Text="" value="" onchange="update()"></asp:TextBox>  

seems I am missing something simple? I also tried using single quotes with <%=InCL.ClientID%>

The alert “hello world” pops-up on change, but not for test…

Using asp.net 3.5, FF, master pages, etc…

Thanks.

EDIT
So I changed it to use this.value and that works, but still no solution in to how to get it by id?

works:

<asp:TextBox ID="InCL" runat="server" Text="" value="1" onchange="update(this.value)"></asp:TextBox>  

with:

function update(x) {

     alert(x);


 }  

Answer 1

The reason this is not working is that the JavaScript is in an external js file that does not go through the processing pipeline and is served statically from disk. The Server side tag <%=InCL.ClientID%> needs to go through the processing pipeline to render out the id string of the server control.

The simplest way to resolve this is to put the script element in the page. Other ways are to define only the JavaScript that has server tags in the page and assign to a global variable. Then define your external script after the global variable declaration and assignment – you can then use this variable in the external script file.