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CountDown react Code Snippet in 2023

componentsstateadvanced

Last Updated: 31 January 2023

Renders a countdown timer that prints a message when it reaches zero.

  • Use the useState() hook to create a state variable to hold the time value. Initialize it from the props and destructure it into its components.
  • Use the useState() hook to create the paused and over state variables, used to prevent the timer from ticking if it's paused or the time has run out.
  • Create a method tick, that updates the time values based on the current value (i.e. decreasing the time by one second).
  • Create a method reset, that resets all state variables to their initial states.
  • Use the the useEffect() hook to call the tick method every second via the use of setInterval() and use clearInterval() to clean up when the component is unmounted.
  • Use String.prototype.padStart() to pad each part of the time array to two characters to create the visual representation of the timer.
const CountDown = ({ hours = 0, minutes = 0, seconds = 0 }) => { const [paused, setPaused] = React.useState(false); const [over, setOver] = React.useState(false); const [[h, m, s], setTime] = React.useState([hours, minutes, seconds]); const tick = () => { if (paused || over) return; if (h === 0 && m === 0 && s === 0) setOver(true); else if (m === 0 && s === 0) { setTime([h - 1, 59, 59]); } else if (s == 0) { setTime([h, m - 1, 59]); } else { setTime([h, m, s - 1]); } }; const reset = () => { setTime([parseInt(hours), parseInt(minutes), parseInt(seconds)]); setPaused(false); setOver(false); }; React.useEffect(() => { const timerID = setInterval(() => tick(), 1000); return () => clearInterval(timerID); }); return ( <div> <p>{`${h.toString().padStart(2, '0')}:${m .toString() .padStart(2, '0')}:${s.toString().padStart(2, '0')}`}</p> <div>{over ? "Time's up!" : ''}</div> <button onClick={() => setPaused(!paused)}> {paused ? 'Resume' : 'Pause'} </button> <button onClick={() => reset()}>Restart</button> </div> ); };
ReactDOM.render( <CountDown hours={1} minutes={45} />, document.getElementById('root') );

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