Download Audio & Video for YouTube v2.6 (MP3, M4V, FULL HD, MP4, FLV, WKV, ACC, etc) - The Best!?

This script helps to add a YouTube download button.
当前为 2018-06-07 提交的版本，查看最新版本。
换行
// ==UserScript==
// @name Download Audio & Video for YouTube v2.6 (MP3, M4V, FULL HD, MP4, FLV, WKV, ACC, etc) - The Best!?
// @description This script helps to add a YouTube download button.
// @namespace https://greasyfork.org/
// @homepageURL https://greasyfork.org/scripts/34613
// @supportURL https://greasyfork.org/scripts/34613/feedback
// @author Punisher
// @version 2.6
// @date 2018-06-07
// @compatible chrome
// @compatible firefox
// @compatible opera
// @compatible safari
// @license GNU GPL v3.0 or later. http://www.gnu.org/copyleft/gpl.html
// @match http*://www.youtube.com/*
// @include http*://*.youtube.com/*
// @include http*://youtube.com/*
// @include http*://*.youtu.be/*
// @include http*://youtu.be/*
// ==/UserScript==

function polymerInject() {
    var buttonDiv = document.createElement("div");
    buttonDiv.id = "downloadButton";

    var subscribeButton = document.querySelector("#subscribe-button paper-button");
    subscribeButton.style.display = "initial";
    subscribeButton.style.width = "170px";

    var addButton = document.createElement("button");
    addButton.appendChild(document.createTextNode("DOWNLOAD"));
    addButton.style.width = "170px";
    addButton.style.position = "relative";
    addButton.style.boxSizing = "border-box";
    addButton.style.minWidth = "5.14em";
    addButton.style.textAlign = "center";
    addButton.style.padding = "10px 16px";
    addButton.style.marginTop = "5px";
    addButton.style.border = "0";
    addButton.style.borderRadius = "2px";
    addButton.style.cursor = "pointer";
    addButton.style.color = "#ffffff";
    addButton.style.backgroundColor = "#3a3a3a";
    addButton.style.fontSize = "1.4rem";
    addButton.style.fontFamily = "inherit";
    addButton.style.fontStyle = "inherit";
    addButton.style.fontWeight = "500";
    addButton.style.textTransform = "uppercase";
    addButton.style.letterSpacing = "0.007px";
    addButton.onclick = function() {

        javascript:(function() {
          var vid = document.location.href;
          if (vid.indexOf('youtube.com')<0) {
            vid = window.prompt('Youtube');
          }
          if (vid && vid.indexOf('youtube.com')) {
            window.open('http://saveclipbro.com/convert?linkToDownload=' + encodeURIComponent(location.href) + '&submit=');
          } else {
            alert('');
          }
        })();
    };
    buttonDiv.appendChild(addButton);

    var targetElement = document.querySelectorAll("[id='subscribe-button']");
    for (var i = 0; i < targetElement.length; i++) {
        if (targetElement[i].className.indexOf("ytd-video-secondary-info-renderer") > -1) {
            targetElement[i].appendChild(buttonDiv);
        }
    }
}

function bugTest(fixBug, textDirection) {
    var likeButton=document.getElementById('watch-like');
    if (likeButton) {
        var spanElements=likeButton.getElementsByClassName('yt-uix-button-content');
    }  
  
    var marginPixels=10, marginPixels=1;
}

setInterval(function() {
    if (document.getElementById("count") && document.getElementById("downloadButton") === null)
        polymerInject();
}, 100);
standardInject();