Tampermonkey / Greasemonkey script to add Language link parameters to Rosettacode Language Category pages

Language_links.user.js

// ==UserScript==
// @name         Language links
// @description  Adds language parameters to category links on Rosettacode.org
// @author       thundergnat
// @namespace    mailto:thundergnat@gmail.com
// @version      0.8
// @updateURL    https://gist.github.com/thundergnat/c5a86a6d5e0018ac67bdea3fc48786a0#file-language_links-user-js
// @downloadURL  https://gist.github.com/thundergnat/c5a86a6d5e0018ac67bdea3fc48786a0#file-language_links-user-js
// @match        *://rosettacode.org/wiki/Category*
// @icon         https://www.google.com/s2/favicons?domain=www.rosettacode.org
// @grant        none
// @run-at       document-end
// ==/UserScript==

// Javascript applet to add language link parameters to Language Category pages
// on Rosettacode.org. By default, task entry links on the Language page just
// point to the top of the task page. This script will add a language link parameter
// to have the link point directly to the specific task entry referred to. No more
// need to scroll half a mile when you follow a link.
//
// Beings I don't know Javascript, and hacked this together with the help of Google,
// W3schools, and stackoverflow, this may be full of bugs and inefficiencies. If you
// spot any, let me know.
// -- thundergnat


// Check to see if the url already has a language link.
function hasLanguageLink(url){ return !!url.match(/#/); }

function addLanguageLinks(Links) {
    for (var i = 0; i < Links.length; i++) { // iterate through the links.
        if(!hasLanguageLink(Links[i].href)) { // if it doesn't already have a language link
            Links[i].setAttribute('href', Links[i].href + '#' + language); // modify the href.
        }
    }
}

// Check to see if the page has an infobox. Pretty much only language category
// pages have one. Avoid modifying other category pages (Programming_tasks,
// Language_users, implementations, examples_needing_attention, Programming_languages, etc).
// If it isn't a Language page, halt further unnecessary processing.
if (!!document.querySelector("div.infobox")) {

    // Locate the page title header
    var header = document.querySelector("span.mw-page-title-main");

    // Grab the page name from the header - nominally the language name,
    // actually the Category name. Massage it a bit into the correct format.
    var language = encodeURIComponent(header.innerHTML.replace(/ /g, "_")).replace(/\%/g, ".");

    // Fix up a few other characters that are legal in uris but Rosettacode doesn't like.
    language = language.replace(/\*/g, ".2A").replace(/\!/g, ".21");

    // Compensate for F# and C# and languages with initial lowercase letter manually.
    var specialCase = {
        "Bc": "bc",
        "C_sharp": "C.23",
        "Dc": "dc",
        "EC": "eC",
        "ElastiC": "elastiC",
        "F_Sharp": "F.23",
        "Ferite": "ferite",
        "Friendly_interactive_shell": "friendly_interactive_shell",
        "Gecho": "gecho",
        "Hexiscript": "hexiscript",
        "I": "i",
        "Jq": "jq",
        "Min": "min",
        "MIRC_Scripting_Language": "mIRC_Scripting_Language",
        "NewLISP": "newLISP",
        "OoRexx": "ooRexx",
        "Sed": "sed",
        "Smart_BASIC": "smart_BASIC",
        "Zkl": "zkl",
        "Icon": "Icon_and_Unicon",
        "Unicon": "Icon_and_Unicon"
    };

    if (language in specialCase) { language = specialCase[language] }

    // Find all of the 'mw-category' divs on the page. Usually there's only one, but
    // languages with 'See also' sections on their Category page have multiple.
    // Lookin' at you Phix and Python...
    var containers = document.querySelectorAll("div.mw-category");

    // Languages with very few examples won't have the 'mw-category' div, use an alternate
    // that all seem to have, but is too broad for languages with more than about 10 examples.
    if(containers.length == 0) {
        containers = document.querySelectorAll("div.mw-content-ltr");
    }

    // Program entries should be in the last container div on the page.
    var container = containers[containers.length - 1];

    // Check to see if container is actually Subcategories div (no task entries) and bail if it is.
    if (container.querySelector("H3").innerHTML === '@') { return }

    // Gather all the relevant links from the container.
    var links = container.querySelectorAll("a");

    window.onload = addLanguageLinks(links); // Add links after the page has loaded.
    setInterval(addLanguageLinks(links), 1000); // Periodically check to see if they need to be updated.

}

Version 0.8 - 2023-01-22

Site updated to MediaWiki 1.39. The page title format changed
slightly. Update code for new format. (It's actually a little less
touchy-feely now, should be a little more robust.)

Version 0.7 - 2021-06-16

Fix typo in specialCase dictionary.

Add fixup for Icon / Unicon task link. They mostly seem to be the
same, vastly more have the composite task link than don't.

Still don't know what to do about Mathematica / Wolfram language
links. I don't even understand why those are listed as two separate
categories. AFAICT, Wolfram language is only used in Mathematica,
and Mathematica only uses Wolfram language. One should just be
a redirect to the other... but what do I know. ¯\_(ツ)_/¯ Whatever.
I'm not going to go nuts trying to compensate for it.

Version 0.6:

Compensate for languages that have an initial lowercase letter in
their name.  Rosettacode (mediawikia) automatically title-cases
category pages,  erroneously upper-casing initial letter of language
name.
    
Compensate with a look-up table of known lower-case names.
I may have missed some.  Still depends on the entry authors
using the correct case in the entry header. If that is wrong all bets
are off. Sed (sed) especially seems to be bad for that. 

Version 0.5:

 Add update and download links.

 Re-arrange logic and tidy a bit. Mostly cosmetic polishing.

Version 0.4:

Use a real encoding function rather than cobbled together bespoke solution.

Fail early and reduce unnecessary work if it is a non-Language Category page.

Better variable names. Cut out some intermediate variables.

Fix bug with languages with no examples getting bogus links

Version 0.3:

 Fix a bunch of typos; mostly but not completely non-functional typos.

Version 0.2:

 Works for most languages.

 Languages with few example aren't picked up correctly.

 Announced publicly.

Version 0.1:

 It sort-of works, but isn't really ready for public consumption.