A React counter app with localStorage

App.js

import { useState, useEffect } from "react";

function App() {
  const key = "count";

  const [count, setCount] = useState(() => {
    const persistedValue = window.localStorage.getItem(key);
    return persistedValue !== null ? JSON.parse(persistedValue) : 0;
  });

  useEffect(() => {
    window.localStorage.setItem(key, JSON.stringify(count));
  }, [count]);

  return (
    <div>
      <h1>Counter</h1>
      <p>Number: {count}</p>
      <button onClick={() => setCount(count - 1)}>-1</button>
      <button onClick={() => setCount(count + 1)}>+1</button>
    </div>
  );
}

export default App;