How to show time and date in realtime in React JS?

Question

Briefing:

Hi, I have created a hook useDate() to display current time and date as follows:

interface ReturnDate {
  time: string;
  date: string;
  wish: string;
}

export const useDate = (): ReturnDate => {
  const locale = 'en';
  const today = new Date();

  const day = today.toLocaleDateString(locale, { weekday: 'long' });
  const date = `${day}, ${today.getDate()} ${today.toLocaleDateString(locale, { month: 'long' })}\n\n`;

  const hour = today.getHours();
  const wish = `Good ${(hour < 12 && 'Morning') || (hour < 17 && 'Afternoon') || 'Evening'}, `;

  const time = today.toLocaleTimeString(locale, { hour: 'numeric', hour12: true, minute: 'numeric' });

  return {
    date,
    time,
    wish,
  };
};

And I'm using it in my component below as follows:

const ProfileGreetings: FC = () => {
  const { firstName } = useUserDetails();
  const { date, time, wish } = useDate();

  return (
    <div className="greetings-container">
      <h1>
        {wish}
        <PrimaryText text={`${firstName || ''}!`} />
      </h1>

      <div>
        <h3>
          {date}
          <br />
          {time}
        </h3>
      </div>
    </div>
  );
};

Date/Time format in app:

Sunday, 2 August

11:54 PM

Problem Statement:

Currently what's happening is that the date and time don't update until I refresh the page. Is there any way to have all of the following to be updated in real time?

I am thinking to use an interval after every 1 minute to compute the updated time and date, but don’t really know if that's good idea. Neither do I know how to start with that and how will the interval be cleared?

Thanks! :)

Answer 1

Since you can use hooks in custom hooks you can create an interval to update every minute like this:

export const useDate = () => {
  const locale = 'en';
  const [today, setDate] = React.useState(new Date()); // Save the current date to be able to trigger an update

  React.useEffect(() => {
      const timer = setInterval(() => { // Creates an interval which will update the current data every minute
      // This will trigger a rerender every component that uses the useDate hook.
      setDate(new Date());
    }, 60 * 1000);
    return () => {
      clearInterval(timer); // Return a funtion to clear the timer so that it will stop being called on unmount
    }
  }, []);

  const day = today.toLocaleDateString(locale, { weekday: 'long' });
  const date = `${day}, ${today.getDate()} ${today.toLocaleDateString(locale, { month: 'long' })}\n\n`;

  const hour = today.getHours();
  const wish = `Good ${(hour < 12 && 'Morning') || (hour < 17 && 'Afternoon') || 'Evening'}, `;

  const time = today.toLocaleTimeString(locale, { hour: 'numeric', hour12: true, minute: 'numeric' });

  return {
    date,
    time,
    wish,
  };
};

Answer 2

I have an idea for this. I will loop on while and dynamic sleep with the difference between currentTime and rounding in seconds of currentTime + 1 second. You can refer to this script.

function getRealTime() {
  const currentTime = Date.now();
  console.log(new Date(Math.round(currentTime / 1000) * 1000), currentTime);
  return (Math.floor(currentTime / 1000) + 1) * 1000 - currentTime;
}

(async function () {
  let reduceTime = 0;
  while (true) {
    reduceTime = getRealTime();
    await sleep(reduceTime);
  }
})()

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}