August 28, 2002 - Sending JavaScript to the Client | WebReference

August 28, 2002 - Sending JavaScript to the Client

Yehuda Shiran August 28, 2002
Sending JavaScript to the Client
Tips: August 2002

Yehuda Shiran, Ph.D.
Doc JavaScript

You can return strings to the client browser with Response.Write(). The output of the Response.Write() statement is incorporated into the page being processed, and displayed at the client browser. Instead of just strings, we can also write scripts with Response.Write(). This script will run on the client browser. It opens the way for popping up message boxes at the client browser, using the client-side JavaScript alert() method. This is how you can pop up windows at the client side from ASP.NET pages running on the server side.

The following ASP.NET page demonstrates how to do it:

  <%@ Page LANGUAGE="JScript" SRC="col116ex7.aspx.js" INHERITS="COL116.codeBehind"
     AutoEventWireup="true" EnableViewState="true"%>
  <HTML>
  <SCRIPT LANGUAGE="JScript" runat="server">
  function popup(str) {
    Response.Write("<script> alert ('" + str + "') </scr" + "ipt>");
  }
  var today : Date = new Date();
  </SCRIPT>
  <HEAD>
    <TITLE>Hello World Test</TITLE>
  </HEAD>
  <BODY STYLE="font-size:12; font-family:arial,verdana,sans-serif;">
    <P ALIGN="center"><% popup("Today is " + today); %></P>
    <FORM RUNAT="server">
    <P ALIGN="center"><ASP:LABEL ID="message" RUNAT="server"></ASP:LABEL></P>
    </FORM>
  </BODY>
</HTML>
We call the popup() function from within the <% %> construct. We concatenate a string ("Today is ") and a variable (today), and pass it to popup(). The popup() function uses Response.Write() to return a script. The script is as follows:

<SCRIPT>
  alert(str);
</SCRIPT>
In order to avoid parsing of the < and > brackets by the server, we split </SCRIPT>, to force their concatenation only at the client side.

Here is the window that pops up at the client side, when setting the URL of the browser to http://localhost/column113/col116ex7.aspx:

To learn more about JScript .NET and ASP.NET, go to Column 116, JScript .NET, Part IX: Displaying Information.