replace settimeout with a worker version that works in the background. even when tab is out of focus. This is not tested across browsers. just works on chromium based browsers.

setTimeoutReplacement.js

;(function (exports) {
	let tid = 0
	const timers = new Map()
	const jsblob = `
const timers = new Map()
const runTimer = function (id) {
	this.postMessage({ id })
	timers.delete(id)
}
this.addEventListener('message', (evt) => {
	let { id, command, timeout } = evt.data
	switch (command) {
		case 'setTimeout':
			timers.set(id, { id, command, timeout })
			setTimeout(runTimer.bind(null, id), timeout | 0)
			break
		case 'clearTimeout':
			if (timers.has(id)) clearTimeout(timers.get(id).id)
			timers.delete(id)
			break
	}
})
`
	const blob = new Blob([jsblob], { type: 'application/javascript' })
	const workerURL = URL.createObjectURL(blob)

	const worker = new Worker(workerURL)
	const oldSetTimeout = setTimeout
	const oldClearTimeout = clearTimeout

	worker.addEventListener('message', function (evt) {
		const { id } = evt.data
		const { fn, args } = timers.get(id)
		fn.apply(null, args)
		timers.delete(id)
	})
	exports.setTimeout = function (fn, timeout = 0) {
		const args = [...arguments].slice(2)
		timers.set(++tid, { fn, args })
		worker.postMessage({ command: 'setTimeout', id: tid, timeout })
		return tid
	}
	exports.clearTimeout = function (id) {
		worker.postMessage({ command: 'clearTimeout', id })
		timers.delete(id)
	}
})(typeof window !== 'undefined' ? window : typeof globalThis !== 'undefined' ? globalThis : {})