Tampermonkey: Redirect Qt5 docs to Qt6 docs

tm-qtdocs.js

// ==UserScript==
// @name     Redirect Qt5 docs to Qt6 docs
// @version  1.0.1
// @author   bindreams
// @match    https://doc.qt.io/qt-5/*
// @run-at   document-start
// @grant    none
// ==/UserScript==

// Check if a url returns 404. Return true if url does not return 404.
function urlExists(url) {
    var req = new XMLHttpRequest();
    req.open('HEAD', url, false);
    req.send();
    return (req.status != 404);
}

var reSuffix = /qt-5\/([\s\S]*)/;

// If regex finds an expected suffix and a matching page on qt-6 exists, redirect
var result = reSuffix.exec(location.pathname);
if (result !== null) {
    var suffix = result[1];
    var url = 'https://doc.qt.io/qt-6/' + suffix;

    if (urlExists(url)) location.replace(url);
}