[GreaseMonkey] App Store / Google Play URL QR Overlay (add QR code link to easily download this app)

appstore-qr-code.js

// ==UserScript==
// @name         App Store / Google Play URL QR Overlay
// @namespace    https://unitycoder.com/
// @version      1.0
// @description  Show a QR code for the current page URL in the top-right corner
// @match        https://apps.apple.com/us/app/*
// @match        https://play.google.com/store/apps/*
// @grant        none
// ==/UserScript==

(function () {
    'use strict';

    var overlayId = 'gm-url-qr-overlay';

    if (document.getElementById(overlayId)) {
        return;
    }

    function addStyles() {
        var style = document.createElement('style');
        style.textContent =
            '#' + overlayId + ' {' +
            'position: fixed;' +
            'top: 75px;' +
            'right: 16px;' +
            'z-index: 2147483647;' +
            'background: rgba(255,255,255,0.96);' +
            'border: 1px solid #ccc;' +
            'border-radius: 10px;' +
            'padding: 10px;' +
            'box-shadow: 0 4px 12px rgba(0,0,0,0.2);' +
            'text-align: center;' +
            'font-family: Arial, sans-serif;' +
            'font-size: 12px;' +
            '}' +
            '#' + overlayId + ' .qr-title {' +
            'margin-bottom: 8px;' +
            'font-weight: bold;' +
            '}' +
            '#' + overlayId + ' img {' +
            'display: block;' +
            'width: 140px;' +
            'height: 140px;' +
            '}';
        document.head.appendChild(style);
    }

    function createOverlay() {
        var overlay = document.createElement('div');
        overlay.id = overlayId;

        var img = document.createElement('img');
        img.alt = 'QR code';
        img.src = 'https://api.qrserver.com/v1/create-qr-code/?size=140x140&data=' + encodeURIComponent(window.location.href);

        overlay.appendChild(img);
        document.body.appendChild(overlay);
    }

    function init() {
        if (!document.body || !document.head) {
            setTimeout(init, 100);
            return;
        }

        addStyles();
        createOverlay();
    }

    init();
})();