Javascript in ASP.net

Philosophaie · 03-05-2013, 03:02 PM

How do you run a Javascript program in ASP.net 4.0 controls.

The old way:
<input id="Button1" type="button" onclick="program();" />

or

<body onload="program();">

ASP.net controls do not accept onclick or onload.

How do you run a Javascript in ASP.net on any control?

Old Pedant · 03-05-2013, 09:27 PM

Well, the best way to do it is the modern "unobtrusive JavaScript" scheme.

Code:

<form id="Form1" runat="server">
<asp:button id="Button1" Text="Something" AutoPostBack="False" />
<asp:button id="Button2" Text="Whatever" AutoPostBack="False" />
...
</form>

<script type="text/javascript">
(
  function( ) /* anonymous master function */
  { 
      // form not needed for this example, but this is what you could use:
      var form = document.getElementById("<%=Form1.clientID %>");

      // for the buttons:
      document.getElementById("<%=Button1.clientID %>").onclick = program;
      document.getElementById("<%=Button2.clientID %>").onclick = program;

      function program( ) 
      { 
          // inside this function, you can refer to the button via this.  Example:
          var buttonValue = this.value; // gets the ASP.Net TEXT property 
          ...
      }

  } // end of master anonymous function
)(); // self-invoke anonymous function
</script>
</body><!-- notice the placement of the script! just before the body's end -->
</html>

CAUTION: If the button is set to do an autopostback, then you can't just assign to the onclick property, as shown. Instead, you would need to use attachEvent (for older MSIE) and/or addEventListener (for newer MSIE and all other browsers). If you do just assign to onclick, as shown above, that would disconnect the autopostback and *ONLY* execute your client-side JS code.