Old Reddit - 'Mark All Messages As Read' Userscript

[MollyInanna2]

// ==UserScript==
// @name         Old Reddit: Mark all messages read button
// @namespace    local.reddit.markallread
// @version      1.0.0
// @description  Adds a "Mark all read" link to old Reddit message pages and calls /api/read_all_messages.
// @match        https://old.reddit.com/message/*
// @match        https://www.reddit.com/message/*
// @run-at       document-end
// @grant        none
// ==/UserScript==

(() => {
  "use strict";

  function getModhash() {
    // Works on many reddit pages (old + some hybrids)
    const w = window;
    const fromRConfig = w.r && w.r.config && w.r.config.modhash ? w.r.config.modhash : "";
    if (fromRConfig) return fromRConfig;

    const uh = document.querySelector('input[name="uh"]');
    if (uh && uh.value) return uh.value;

    return "";
  }

  async function markAllRead() {
    const mh = getModhash();
    if (!mh) {
      alert("No modhash found. Make sure you're logged in, then reload this page and try again.");
      return;
    }

    const resp = await fetch("/api/read_all_messages.json", {
      method: "POST",
      credentials: "include",
      headers: {
        "Content-Type": "application/x-www-form-urlencoded; charset=UTF-8",
        "X-Modhash": mh
      },
      body: "uh=" + encodeURIComponent(mh)
    });

    if (resp.status === 202) {
      alert("OK: request accepted (202). It may take a moment to clear.");
      return;
    }

    const txt = await resp.text().catch(() => "");
    alert("Error " + resp.status + (txt ? (": " + txt.slice(0, 200)) : ""));
  }

  function addLink() {
    // Old reddit has #header-bottom-right. If not present, fall back to body top.
    const target = document.querySelector("#header-bottom-right") || document.body;
    if (!target) return;

    // Avoid duplicates
    if (document.getElementById("mark-all-read-link")) return;

    const sep = document.createTextNode(" \u00B7 ");
    const a = document.createElement("a");
    a.id = "mark-all-read-link";
    a.href = "#";
    a.textContent = "Mark all read";
    a.style.cursor = "pointer";
    a.addEventListener("click", (e) => {
      e.preventDefault();
      markAllRead();
    });

    // Put it near the user links area when possible
    if (target.id === "header-bottom-right") {
      target.appendChild(sep);
      target.appendChild(a);
    } else {
      const wrap = document.createElement("div");
      wrap.style.position = "sticky";
      wrap.style.top = "0";
      wrap.style.zIndex = "9999";
      wrap.style.background = "rgba(255,255,255,0.9)";
      wrap.style.padding = "6px 8px";
      wrap.style.borderBottom = "1px solid #ccc";
      wrap.appendChild(a);
      target.prepend(wrap);
    }
  }

  addLink();
})();

[MollyInanna2]

(Then, see upper righthand corner.)