always on focus.js

// ==UserScript==
// @name         Always On Focus
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description Prevent websites from detecting when you switch tabs or unfocus the window
// @author       You
// @match        *://*/*
// @grant        none
// ==/UserScript==

(function() {
    // Store the initial state of document.hasFocus
    const originalHasFocus = document.hasFocus;

    // Override document.hasFocus based on window focus
    window.addEventListener('focus', function() {
        document.hasFocus = function() { return true; };
    });

    window.addEventListener('blur', function() {
        document.hasFocus = function() { return false; };
    });

    // Restore the original behavior after the script runs
    setTimeout(function() {
        document.hasFocus = originalHasFocus;
    }, 0);
})();