timer.js

const length =  10 * 1000 * 60;
const App: React.FC = () => {
  const timer = useTimer({ length });
  return (
    <div className="App">
      <h2>{timer.value}</h2>
      <div>
        <Button onClick={timer.start}>Start</Button>
        <Button onClick={timer.stop}>Stop</Button>
        <Button onClick={timer.skip}>Skip</Button>
        <Button onClick={timer.reset}>Reset</Button>
      </div>
    </div>
  );
}