--> The technicals which will use in this program (React.js, React Hooks - useState).

The program..
1) add:

import React, {useState} from "react";

2) add function which name the same for the file e.g// App

function App() {

setInterval(sayHi, 1000) --> This function prints sayHi every second, but you will add setInterval(updatetime, 1000);

const now = new Date(); --> This is the object for the Date. For example// you can get the hour when you write const now = new Date ().getHours();, but here you want full-time (( hour: min: sec AM/PM )) for that, will use:
const now = new Date().toLocaleTimeString();

3) add hooks:

const [time,setTime] = useState(now);

4) update function time:

function updatetime() {
    const newtime = new Date().toLocaleTimeString();
    setTime(newtime);
  }

5) Program output to the user:

return(
    <div>
      <h1>{time}</h1>
    </div>
);

Final file will be 🎈:

😍
Thank you..