2ch.sortbyreply.user.js

// ==UserScript==
// @name         2ch.hk | Сортировка по ответам
// @version      0.1
// @match        ://2ch.hk/*/res/*.html
// @icon         https://2ch.hk/favicon.ico
// @grant        none
// ==/UserScript==

(function () {
    "use strict";

    function reply_count($post) {
        return $post.querySelector(".post__refmap").childElementCount;
    }

    document
        .querySelector(".thread-nav__inner")
        .insertAdjacentHTML(
        "beforeend",
        ' | <span><input type="checkbox" id="sort-checkbox"> Сортировать по ответам</span>'
    );

    const $thread = document.querySelector(".thread");
    //$thread.style.display = "flex";
    $thread.style["flex-direction"] = "column";
    $thread.children[0].style.order = -1000; // fix op-post

    document.querySelector("#sort-checkbox").addEventListener("change", (el) => {
        if (el.target.checked) {
            $thread.style.display = "flex";
            const posts = document.querySelectorAll(".thread__post");
            posts.forEach(($post) => {
                $post.style.order = -reply_count($post);
            });
        } else {
            $thread.style.display = "block";
        }
    });
})();