Something like this
Code:
<script language="javascript" type="text/javascript" >
<!--
function my()
{
var var1;
var1=document.getElementsById("Text1");
// Use Var1 to be put into something else.
}
-->
</script>
<form id="form1" runat="server">
<input id="Text1" type="text" name="name_txt" value="1234567890"/>
<input id="Button1" type="button" value="button" onclick="my()"/>
</form>
Use Var1 to be put into something else.