Simple countdown

A. Simple Countdown.md

Simple Countdown

Countdown.jsx

import { useEffect, useRef, useState } from 'react';

const GIVEN_TIME = 20;
const adjustedTimeInMillis = GIVEN_TIME * 1000 * 60;
const formatTime = (time) => time < 10 ? `0${time}` : time;

const App = () => {
  const [millis, setMillis ] = useState(adjustedTimeInMillis);
  const minutes = Math.floor(millis / 1000 / 60) % 60;
  const seconds = Math.floor(millis / 1000) % 60;

  const interval = useRef(null);

  const countDown = () => {
    setMillis((time) => {
      if (time === 0) {
        return time
      }
      const timeLeft = time - 1000;
     return timeLeft;
    })
  };

  useEffect(() => {
    interval.current = setInterval(countDown, 1000);
    return () => clearInterval(interval.current);
  }, [])
  return (
    <div>Coucou: {formatTime(minutes)}:{formatTime(seconds)}</div>
  );
}

export default App;