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Warns with a pop-up if signed into Google / YouTube
// ==UserScript==
// @name GoogleIsWatchingYou
// @namespace https://openuserjs.org/users/sammcj
// @version 0.3
// @description Warns with a pop-up if signed into Google / YouTube
// @author Sam McLeod
// @twitter https://twitter.com/s_mcleod
// @copywrite 2018, Sam McLeod
// @license MIT
// @include /^https?://www\.google\.com.*/.*$/
// @include /^https?://www\.youtube\.com.*/.*$/
// @exclude /^https?://www.google.com/recaptcha/.*
// @grant metadata
// ==/UserScript==
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Introduction_to_using_XPath_in_JavaScript
var xpathResult = document.evaluate('count(//*[@id="gb_70"])', document, null, XPathResult.ANY_TYPE, null);
if (xpathResult.numberValue === 0) {
alert("WARNING: You are signed into Google!");
}