Greasemonkey: Re-write all links based on param - greasemonkey

Question

I need alittle help with getting a script that will take param from the orginal link and re-write them into a new link. I guess it should be pretty easy but I'm a noob still when it comes to this.
Here is the orginal HTML code for 1 link. (should be replaced globaly on the page. image1.jpg, image2.jpg etc.)
<div align="center"><img src="/preview/image1.jpg" width="128" height="128" border="0" style="border: 0px black solid;" /></div>
This should be done global on all the links that contain the imagepath "/preview/"
Thanks to Brock Adams I kinda understand how to get the param values with this code but I still don't really get it how to re-write all the links in a page.
var searchableStr = document.URL + '&';
var value1 = searchableStr.match (/[\?\&]id=([^\&\#]+)[\&\#]/i) [1];
var value2 = searchableStr.match (/[\?\&]connect=([^\&\#]+)[\&\#]/i) [1];
and then rewrite the links with "newlink"
var domain = searchableStr.match (/\/\/([w\.]*[^\/]+)/i) [1];
var newlink = '//' + domain + '/' + value1 + '/data/' + value2 + '.ext';
If someone could be so nice to help me setup an example greasemonkey script I would be very greatful for it.

Answer 1

OK, This is a fairly common task and I don't see any previous, Stack Overflow questions like it -- at least in a 2 minute search.
So, here's a script that should do what you want, based on the information provided...
// ==UserScript==
// #name Site_X, image relinker.
// #namespace StackOverflow
// #description Rewrites the preview links to ???
// #include http://Site_X.com/*
// #include http://www.Site_X.com/*
// #include https://Site_X.com/*
// #include https://www.Site_X.com/*
// ==/UserScript==
function LocalMain () {
/*--- Get all the images that have /preview/ in their path.
*/
var aPreviewImages = document.evaluate (
"//img[contains (#src, '/preview/')]",
document,
null,
XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,
null
);
var iNumImages = aPreviewImages.snapshotLength;
GM_log (iNumImages + ' preview images found.');
/*--- Rewrite the parent links to our new specifications.
Note, all the target links are of the form:
<a href="/index.php?Submit=ok&seson=b1e4&connect=127.0.0.1&id=13033&name=on">
<img src="/preview/image1.jpg" width="128" height="128" border="0" style="border: 0px black solid;" />
</a>
The desired rewrite changes the link to this form:
<a href="{current page's domain}/{id-value}/data/{connect-value}.ext">
*/
for (var iLinkIdx=0; iLinkIdx < iNumImages; iLinkIdx++) {
var zThisImage = aPreviewImages.snapshotItem (iLinkIdx);
var zParentLink = zThisImage.parentNode;
//--- Get the key href parameters.
var sIdValue = sGetUrlParamValue (zParentLink, 'id');
if (!sIdValue) continue; //-- Oopsie, this link was a malformed.
var sConnectValue = sGetUrlParamValue (zParentLink, 'connect');
if (!sConnectValue) continue;
//--- Get the current page's domain. (Or just use a relative link.)
var sPageDomain = document.URL.match (/\/\/([w\.]*[^\/]+)/i) [1];
//--- Generate the desired link value.
var sDesiredLink = 'http://' + sPageDomain + '/' + sIdValue + '/data/' + sConnectValue + '.ext';
//--- Rewrite the target link.
zParentLink.href = sDesiredLink;
}
}
function sGetUrlParamValue (zTargLink, sParamName) {
var zRegEx = eval ('/[\?\&]' + sParamName + '=([^\&\#]+)[\&\#]/i');
var aMatch = (zTargLink.href + '&').match (zRegEx);
if (aMatch)
return decodeURI (aMatch[1]);
else
return null;
}
window.addEventListener ("load", LocalMain, false);