Greasemonkey / Violentmonkey userscript for day, evening and night color schemes

Dark.user.js

// ==UserScript==
// @name          Dark Reader (Unofficial)
// @icon          https://darkreader.org/images/darkreader-icon-256x256.png
// @namespace     DarkReader
// @description      Inverts the brightness of pages to reduce eye strain
// @version       4.7.15
// @author        https://github.com/darkreader/darkreader#contributors
// @homepageURL   https://darkreader.org/ | https://github.com/darkreader/darkreader
// @run-at        document-end
// @grant         none
// @include       http*
// @require       https://cdn.jsdelivr.net/npm/darkreader/darkreader.min.js
// @noframes
// ==/UserScript==

const isFirefox = window.navigator.userAgent.toLowerCase().indexOf('firefox') > -1;

function update(state) {
    const now = new Date().getHours();

    const isMorning = now > 5 && now <= 12;
    const isAfternoon = now > 12 && now <= 18;
    const isEarlyEvening = now > 18 && now <= 22;
    const isLateEvening = now > 22 && now <= 23;
    const isNight = now > 23 || now <= 5;

    const isDay = isMorning || isAfternoon;
    const isDayOrEarlyEvening = isDay || isEarlyEvening;
    const newState = [isDayOrEarlyEvening, isLateEvening, isNight];

    if (JSON.stringify(state) != JSON.stringify(newState)) {
        if (isDayOrEarlyEvening) {
            console.log('day or early evening');
            if (isFirefox) {
                DarkReader.enable({
                    brightness: 100,
                    contrast: 100,
                    sepia: 0
                });
            } else {
                DarkReader.disable();
            }
        } else if (isLateEvening) {
            console.log('late evening');
            DarkReader.enable({
                brightness: 100,
                contrast: 85,
                sepia: 30
            });
        } else if (isNight) {
            console.log('night');
            DarkReader.enable({
                brightness: 100,
                contrast: 85,
                sepia: 100
            });
        }
    }
    return newState;
}

function mainLoop(state, timeout) {
    setTimeout(function() {
        mainLoop(update(state));
    }, timeout);
}

let current_host = new URL(document.URL);
if (current_host.hostname == 'localhost' && current_host.port == 7171) {
    console.log('ignore this URL');
} else {
    if (isFirefox) {
        window.addEventListener('load', function() {
            mainLoop([], 100);
        }, true);
    } else {
        mainLoop(update([]), 60 * 1000);
    }
}