youtube-disable-polymer.js

// ==UserScript==
// @name         YouTube disable polymer
// @namespace    https://zackguard.com/
// @version      0.0.1
// @description  Disable Polymer on all YouTube pages
// @author       Zack Guard
// @match        https://www.youtube.com/*
// @run-at       document-start
// @grant        none
// ==/UserScript==

(function() {
    "use strict";

    const url = new URL(window.location);
    if (url.searchParams.get("disable_polymer") !== "1") {
        url.searchParams.append("disable_polymer", "1");
        window.location.href = url.toString();
    }

    document.addEventListener("mouseover", e => {
        const target = e.target;
        let linkElem;
        if (target.tagName === "A" && target.href) {
            linkElem = target;
        } else if (target.classList.contains("title") && target.parentElement.tagName === "A" && target.parentElement.href) {
            linkElem = target.parentElement;
        } else if (
            target.tagName === "IMG" && target.parentElement.classList.contains("yt-thumb-simple")
            || target.classList.contains("mouseover-img")
            || target.classList.contains("masthead-logo-renderer-logo")
        ) {
            linkElem = target.closest("a");
        }
        if (linkElem) {
            const url = new URL(linkElem.href);
            if (url.searchParams.get("disable_polymer") !== "1") {
                url.searchParams.append("disable_polymer", "1");
                linkElem.href = url.toString();
            }
        }
    });
})();