I have a GM_xmlhttpReqeust function setup as follows (simplified version) in my Greasemonkey script.

  GM_xmlhttpRequest({
    synchronous: false,
    method: "HEAD",
    url: "http://www.example1.com",
    onload: function(response){console.debug(url);},
  });

• GM_xmlhttpReqeust is called in asynchronous mode in my code.

• Once accessed, http://www.example1.com does a 302 redirect to http://www.example2.com

• I would like to access the value of the original url parameter (http://www.example1.com) inside onload callback function.

• As per GM_xmlhttpReqeust documentation, http://www.example2.com can be found in response.finalUrl inside onload callback.

Could someone please point me to the proper Greasemonkey/JavaScript way?

The response passed to onload is an object with these key properties:

• readyState
• responseHeaders
• responseText
• status
• statusText
• finalUrl

You want finalUrl, you get it like:

GM_xmlhttpRequest ( {
    synchronous:    false,
    method:         "HEAD",
    url:            "http://www.google.com",
    onload:         function (response) {
        console.debug (response.finalUrl);
    }
} );

---

---

Update for revised/clarified question:

In order to get/know the originally requested URL, you must call GM_xmlhttpRequest() in a closure. Like so:

var origURL = "http://www.google.com";

(function (targURL) {
    GM_xmlhttpRequest ( {
        synchronous:    false,
        method:         "HEAD",
        url:            targURL,
        onload:         function (response) {
            console.log ("orig URL: ", targURL);
            console.log ("final URL: ", response.finalUrl);
        }
    } );
} ) (origURL);