4chan Session ID Unbreaker

Tries to detect and un-break Session IDs posted on 4chan
As of 2024-02-26. See the latest version.
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// ==UserScript==
// @name         4chan Session ID Unbreaker
// @license      GPLv3
// @namespace    https://boards.4chan.org/
// @version      1.3
// @description  Tries to detect and un-break Session IDs posted on 4chan
// @author       ceodoe
// @match        https://boards.4chan.org/*/thread/*
// @match        https://boards.4chan.org/*/res/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=4chan.org
// @grant        none
// ==/UserScript==

function parsePosts() {
    let posts = document.querySelectorAll("blockquote.postMessage");
    for(let i = 0; i < posts.length; i++) {
        if(posts[i].getAttribute("data-4sidu-parsed") !== "1") {
            posts[i].setAttribute("data-4sidu-parsed", "1");

            // Strip all backlinks as they are likely to contain the magic number 05 that all Session IDs start with
            let postText = posts[i].innerText.replace(/\>\>\b[0-9]+\b/g, "");
            let idStartIndex = postText.indexOf("05");

            if(idStartIndex > -1) {
                let id = postText.substring(idStartIndex).replace(/[^A-Fa-f0-9]/g, "").substring(0, 66);

                if(id.length == 66) { // All Session IDs are 66 characters long; if we didn't get that many characters, the ID is invalid
                    let html = `
                        <div style="margin-top: 1em; border-top: 1px solid; padding: 0.5em; width: fit-content;">
                            <span style="color: #66cc33; font-weight: bold;">Session ID:</span> ${id}
                        </div>
                    `;

                    posts[i].insertAdjacentHTML("beforeend", html);
                }
            }
        }
    }
}

new MutationObserver(function(event) { parsePosts(); }).observe(document.querySelector("div.thread"), {childList: true});
parsePosts();