Example of a React Counter with localStorage - https://www.youtube.com/@pH7Programming

CounterApp.jsx

import {useEffect, useState} from 'react'
import './App.css'

export const CounterApp = () => {

    const storageKeyName = "count";

    const retrieveCountValue = () => Number(localStorage.getItem(storageKeyName) || 0);

    const [count, setCount] = useState(retrieveCountValue());
    const addNumber = (count) => setCount(Number(count) + 1);

    useEffect(() => {
        localStorage.setItem(storageKeyName, String(count));
    }, [count]);

    return (
        <div className="App">
            Count Me

            <button onClick={() => addNumber(count)}>
                count is {count}
            </button>
        </div>
    )
}