firstProject

createButtonForDownloadYoutubeVideo
Versión del día 31/1/2020. Echa un vistazo a la versión más reciente.
Pregunta tus dudas, ponle nota o notifica una posible infracción de las normas.
Ajuste de línea
// ==UserScript==
// @name         firstProject
// @namespace    https://up.mewf.ru/
// @version      0.3
// @description  createButtonForDownloadYoutubeVideo
// @author       Klastor
// @match        https://www.youtube.com/*
// @grant        none
// ==/UserScript==
(function() {
    console.log("запустилассь функция");
    localStorage.setItem("linkNow", "https://www.youtube.com");
    window.addEventListener("hashchange", test());
    function test() {
        console.log("запустилассь функция test");

        if (localStorage.getItem("linkNow") != window.location.href) {
            console.log("зашли в иф функции тест");
            localStorage.setItem("oldLink", localStorage.getItem("linkNow"));
            localStorage.setItem("linkNow", window.location.href);
            let links = window.document.location.href.replace("w.y", "w.ssy");
            createButton(links);
        } else {
            console.log("елс функции тест");
            setTimeout(test, 60000);
        }
    }
    function createButton(links) {
        console.log("запустилассь функция links");

        if (!document.getElementsByTagName("butn")) {
            console.log("зашли в иф функция links");

            let btn = document.createElement("a");
            btn.href = links;
            btn.target = "_blank";
            btn.name = "butn";
            btn.title = "Скачать видео";
            //<!-- _______________________________________________________ -->
            let image = document.createElement("img");
            image.src =   "data:image/svg+xml;base64,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";
            image.name = "icon";
            image.alt = "download-icon";
            image.style.objectFit = "contain";
            image.style.height = "24px";
            image.style.width = "24px";
            image.style.borderRadius = "10px";
            //<!-- _______________________________________________________ -->
            let pismo = document.createElement("p");
            pismo.innerHTML = "скачать";
            pismo.setAttribute("style","width: 65px;float:right;text-decoration: none;font-size: 1.3rem;font-weight: 500;display: block;overflow: hidden;text-overflow: ellipsis;white-space: nowrap;text-transform: uppercase;letter-spacing: -1px;color: #606060");
            //<!-- _______________________________________________________ -->
            btn.append(image);
            btn.append(pismo);
            document.querySelector("menu-container").insertAdjacentElement("beforeBegin", btn);
        } else {
            console.log("зашли в елс функция links");
            let btn2 = document.getElementsByTagName("butn");
            btn2.href = links;
            console.log(btn2);
        }
    }
})();