Active chatters count Twitch (Tampermonkey)

// ==UserScript==
// @name         Twitch unique active chatters count
// @namespace    http://tampermonkey.net/
// @version      0.2
// @description  Ilyukha Mad Baza
// @author       Tredovsky
// @match        https://www.twitch.tv/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=twitch.tv
// @grant        none
// @updateURL    https://pastebin.com/raw/xbtgiN8v
// @downloadURL  https://pastebin.com/raw/xbtgiN8v
// ==/UserScript==

(function() {
    'use strict';
    let date = new Date().toLocaleString();
    const UPDATE_PERIOD_MS = 3000;
    let nameSet = new Set();
    let chattersCountEl;
    let streamerPathname = window.location.pathname;

    setInterval(() => {
        const nameElements = document.getElementsByClassName('chat-author__display-name');
        const names = [...nameElements].map(ne => ne.innerText);

        if (window.location.pathname === streamerPathname) {
          nameSet = nameSet.union(new Set(names));
        } else {
          nameSet = new Set(names);
          date = new Date().toLocaleString();
          streamerPathname = window.location.pathname;
        }

        console.log(`Unique chatters in chat: ${nameSet.size}`);

        const viewerCountEl = document.querySelector('[data-a-target="animated-channel-viewers-count"]')?.parentElement;
        if (!viewerCountEl) return;
        if (chattersCountEl && viewerCountEl.contains(chattersCountEl)) viewerCountEl.removeChild(chattersCountEl);
        chattersCountEl = document.createElement('p');
        chattersCountEl.innerText = `(${nameSet.size})`;
        chattersCountEl.title = `Начиная с ${date}`;
        viewerCountEl.appendChild(chattersCountEl);
    }, UPDATE_PERIOD_MS);
})();