Injecting JavaScript into head element of website using Fiddler

Question

I was thinking of using Fiddler for the following purpose...

I have a JavaScript based service I want to demonstrate to potential clients. In order to show them wha

Answer 1

if you use jQuery you can add js on the fly. I would probably think you can have a method which would include/exclude your script based on some query param. This is how you would include JS with jQuery

$.getScript('someScript.js',function(){
//Do something here after your script loads
});

Answer 2

Haven't tried it, but how about GreaseMonkey for IE?

Answer 3

Open fiddler -> Menu Rules -> Customize Rules (or hit Ctrl+R)

The CustomRule.js file opens. Scroll down until you find the line

static function OnBeforeResponse(oSession: Session)

This is where your code goes. Here you can change the server response before the browser sees it.

The following code sample shows how to include a custom piece of jQuery code which replaces the Unanswered link in the horizontal menu with a link which serves as short cut to Unanswered jQuery Questions

I first show you the jQuery code I want to include

<script type='text/javascript'>
    $(function() {
        var newLink = '<a href="/unanswered/tagged/jquery">Unanswered jQuery</a>';
        $('div#hmenus div.nav:first ul li:last a').replaceWith(newLink);
    });
</script>

Now the fiddler code (based on code found in CustomRules.js and code samples from the FiddlerScript CookBook)

//is it a html-response and is it from stackoverflow.com
if (oSession.oResponse.headers.ExistsAndContains("Content-Type", "html") &&
    oSession.HostnameIs("stackoverflow.com")) {

    // Remove any compression or chunking
    oSession.utilDecodeResponse();

    var oBody = System.Text.Encoding.UTF8.GetString(oSession.responseBodyBytes);

    // Match the jQuery script tag
    var oRegEx = /(<script[^>]*jquery.min.js"><\/script>)/gi;
    // replace the script tag withitself (no change) + append custom script tag
    oBody = oBody.replace(oRegEx, "$1<script type='text/javascript'>$(function() {$('div#hmenus div.nav:first ul li:last a').replaceWith('<a href=\"/unanswered/tagged/jquery\">Unanswered jQuery</a>');})</script>");

    // Set the response body to the changed body string
    oSession.utilSetResponseBody(oBody); 
}

I think you should now able to hackyourself together a piece of code which fits your problem.

Example

// Match the head end
var oRegEx = /(<\/head>)/gi;
// replace with new script
oBody = oBody.replace(oRegEx, "<script type='text/javascript' src='http://url/myscript.js'></script>$1");