ReactJs — useEffect Hook
useEffect
is used to perform side effects in functional components, such as fetching data, updating the DOM, or setting up timers. It runs after the component renders.
import React, { useEffect, useState } from 'react';
function Timer() {
const [seconds, setSeconds] = useState(0);
useEffect(() => {
const interval = setInterval(() => setSeconds(sec => sec + 1), 1000);
return () => clearInterval(interval); // Cleanup
}, []);
return <p>Seconds elapsed: {seconds}</p>;
}
export default Timer;