YouTube budget.js

// ==UserScript==
// @name         YouTube budget
// @version      0.1.2
// @description  Budgets YT time
// @author       Patrick Bowen
// @match        https://www.youtube.com/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=youtube.com
// @grant        none
// ==/UserScript==

const minutes = 20;

//Storing the last time since all videos were paused
const save = n => localStorage.setItem('YT', n);
const load = () => new Date(Number(localStorage.getItem('YT')));
let previousCreditMs = null;

(function() {
    if (GM_info.isIncognito) {
        return;
    }
    setInterval(() => {
        const vid = document.querySelector('#movie_player video');
        if (!vid) {
            return;
        }

        const debitMs = Number(!vid.paused) * 2_000;
        const time = load();
        const creditMs = Math.max(Math.min(Date.now() - time, 1_000 * 60 * minutes), 0);
        if (!previousCreditMs) previousCreditMs = creditMs;
        document.title = `${Math.floor(creditMs / 1_000)}s ${document.title.replace(/^[0-9s]+? /, '')}`;

        //Pause video if we have fewer than a second of credit remaining, or if two videos are playing at once
        if (creditMs <= 1000 || (previousCreditMs - creditMs) > 1_500) {
            vid.pause();
        }
        previousCreditMs = creditMs;

        save(Date.now() - creditMs + debitMs);
    }, 1000);
})();