MeFi Navigator Redux

MetaFilter: navigate through users' comments, and highlight comments by OP and yourself
Wrap lines
// ==UserScript==
// @name         MeFi Navigator Redux
// @namespace    https://github.com/klipspringr/mefi-userscripts
// @version      2025-04-10
// @description  MetaFilter: navigate through users' comments, and highlight comments by OP and yourself
// @author       Klipspringer
// @supportURL   https://github.com/klipspringr/mefi-userscripts
// @license      MIT
// @match        *://*.metafilter.com/*
// @grant        none
// ==/UserScript==
 
const SVG_UP = `<svg xmlns="http://www.w3.org/2000/svg" hidden style="display:none"><path id="mfnr-up" fill="currentColor" d="M 0 93.339 L 50 6.661 L 100 93.339 L 50 64.399 L 0 93.339 Z" /></svg>`;
const SVG_DOWN = `<svg xmlns="http://www.w3.org/2000/svg" hidden style="display:none"><path id="mfnr-down" fill="currentColor" d="M 100 6.69 L 50 93.31 L 0 6.69 L 50 35.607 L 100 6.69 Z" /></svg>`;
 
const ATTR_BYLINE = "data-mfnr-byline";
const ATTR_NAVIGATOR = "data-mfnr-nav";
 
const getCookie = (key) => {
    const s = RegExp(key + "=([^;]+)").exec(document.cookie);
    if (!s || !s[1]) return null;
    return decodeURIComponent(s[1]);
};
 
const markSelf = (targetNode) => {
    const span = document.createElement("span");
    span.style["margin-left"] = "4px";
    span.style["padding"] = "0 4px";
    span.style["border-radius"] = "2px";
    span.style["background-color"] = "#C8E0A1";
    span.style["color"] = "#000";
    span.style["font-size"] = "0.8em";
    span.textContent = "me";
    targetNode.after(span);
};
 
const markOP = (targetNode) => {
    const wrapper = targetNode.parentNode.parentNode;
    wrapper.style["border-left"] = "5px solid #0004";
    wrapper.style["padding-left"] = "10px";
};
 
const createLink = (href, svgHref) => {
    const a = document.createElement("a");
    a.setAttribute("href", "#" + href);
    const svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
    svg.setAttribute("width", "1em");
    svg.setAttribute("viewBox", "0 0 100 100");
    svg.setAttribute("style", "vertical-align: middle; top: -1px;");
    const use = document.createElementNS("http://www.w3.org/2000/svg", "use");
    use.setAttribute("href", "#" + svgHref);
    svg.appendChild(use);
    a.appendChild(svg);
    return a;
};
 
const processByline = (
    bylineNode,
    user,
    anchor,
    anchors,
    firstRun,
    self = null,
    op = null
) => {
    // don't mark self or OP more than once
    if (firstRun || !bylineNode.hasAttribute(ATTR_BYLINE)) {
        if (self !== null && user === self) markSelf(bylineNode);
        if (op !== null && user === op) markOP(bylineNode);
        bylineNode.setAttribute(ATTR_BYLINE, "");
    }
 
    if (anchors.length <= 1) return;
 
    const i = anchors.indexOf(anchor);
    const previous = anchors[i - 1];
    const next = anchors[i + 1];
 
    const navigator = document.createElement("span");
    navigator.setAttribute(ATTR_NAVIGATOR, "");
 
    const nodes = ["["];
    if (previous) nodes.push(createLink(previous, "mfnr-up"));
    nodes.push(anchors.length);
    if (next) nodes.push(createLink(next, "mfnr-down"));
    nodes.push("]");
 
    navigator.append(...nodes);
    bylineNode.parentElement.appendChild(navigator);
};
 
const run = (firstRun = false) => {
    const start = performance.now();
 
    const subsite = window.location.hostname.split(".")[0];
    const opHighlight = subsite !== "ask" && subsite !== "projects"; // don't highlight OP on subsites with this built in
    const self = getCookie("USER_NAME");
 
    // if not first run, remove any existing navigators (from both post and comments)
    if (!firstRun) {
        document
            .querySelectorAll(`span[${ATTR_NAVIGATOR}]`)
            .forEach((n) => n.remove());
    }
 
    // post node
    // tested on all subsites, modern and classic, 2025-04-10
    const postNode = document.querySelector(
        "div.copy > span.smallcopy > a:first-child"
    );
    const op = postNode.textContent;
 
    // initialise with post
    const bylines = [[op, "top"]];
    const mapUsersAnchors = new Map([[op, ["top"]]]);
 
    // comment nodes, excluding live preview
    // tested on all subsites, modern and classic, 2025-04-10
    const commentNodes = document.querySelectorAll(
        "div.comments:not(#commentform *) > span.smallcopy > a:first-child"
    );
 
    for (const node of commentNodes) {
        const user = node.textContent;
 
        const anchorElement =
            node.parentElement.parentElement.previousElementSibling;
        const anchor = anchorElement.getAttribute("name");
 
        bylines.push([user, anchor]);
 
        const anchors = mapUsersAnchors.get(user) ?? [];
        mapUsersAnchors.set(user, anchors.concat(anchor));
    }
 
    for (const [i, bylineNode] of [postNode, ...commentNodes].entries()) {
        processByline(
            bylineNode,
            bylines[i][0],
            bylines[i][1],
            mapUsersAnchors.get(bylines[i][0]),
            firstRun,
            self,
            opHighlight && i > 0 ? op : null
        );
    }
 
    console.log(
        "mefi-navigator-redux",
        firstRun ? "first-run" : "new-comments",
        1 + commentNodes.length,
        Math.round(performance.now() - start) + "ms"
    );
};
 
(() => {
    if (
        !/^\/(\d|comments\.mefi)/.test(window.location.pathname) ||
        /rss$/.test(window.location.pathname)
    )
        return;
 
    document.body.insertAdjacentHTML("beforeend", [SVG_UP, SVG_DOWN].join(""));
 
    const newCommentsElement = document.getElementById("newcomments");
    if (newCommentsElement) {
        const observer = new MutationObserver(() => run(false));
        observer.observe(newCommentsElement, { childList: true });
    }
 
    run(true);
})();
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