====== Substitute HTML or JavaScript on the fly ======

Using this recipe - while browsing a remote server - you can trick your browser into taking one file (JavaScript, HTML, image, ecc.) from a web server controlled by you, instead of from the original server.

This can be useful to test some changes on a production server without actually touching the deployed code.

It works by telling the browser to use a proxy for a particular URL, and configure a fake web server to serve that content, eventually canged.

Create a file **''proxy.pac''** and store it into your web server:

<code javascript>
function FindProxyForURL(url, host) {
    if (shExpMatch(url, "http://remote.server.com:8084/subdir/page.jsp?query_string")) {
        return "PROXY your.server.org:8084";
    }
}
</code>

Configure a fake ''VirtualHost'' on your web server:

<file>
NameVirtualHost *:8084
Listen 8084

<VirtualHost *:8084>
    ServerName remote.server.com
    DocumentRoot /var/www/remote.server.com
    ServerAdmin webmaster@rigacci.org
    ErrorLog /var/log/apache2/remote.server.com/error.log
    CustomLog /var/log/apache2/remote.server.com/access.log combined

    # Force .jsp to be served as HTML
    AddType text/html .jsp

    <Directory /var/www/remote.server.com>
        AllowOverride All
    </Directory>
</VirtualHost>
</file>

Then put the fake file into the DocumentRoot for the VirtaulHost. In the example above it will be **''/var/www/remote.server.com/subdir/page.jsp''**.

Configure the browser to use automatic proxy configuration, and give **''%%http://your.server.org/proxy.pac%%''** as the URL.

**NOTE:** This trick **does not work with Internet Explorer**, because it caches the proxy configuration on a per-server basis. If one page from the server was got via proxy, all the subsequent pages will be too.