Persisting State with useLocalStorage

import { useState, useEffect } from 'react';

const useLocalStorage = (key, initialValue) => {
  const [storedValue, setStoredValue] = useState(() => {
    try {
      const item = window.localStorage.getItem(key);
      return item ? JSON.parse(item) : initialValue;
    } catch (error) {
      console.warn(`Error reading localStorage key “${key}”:`, error);
      return initialValue;
    }
  });

  const setValue = (value) => {
    try {
      const valueToStore = value instanceof Function ? value(storedValue) : value;
      setStoredValue(valueToStore);
      window.localStorage.setItem(key, JSON.stringify(valueToStore));
    } catch (error) {
      console.error(`Error writing to localStorage key “${key}”:`, error);
    }
  };

  useEffect(() => {
    // This effect ensures that if initialValue changes, we update storedValue
    // only if the item doesn't exist in localStorage yet.
    // If it exists, we stick to what's in localStorage.
    try {
      const item = window.localStorage.getItem(key);
      if (!item) {
        window.localStorage.setItem(key, JSON.stringify(initialValue));
        setStoredValue(initialValue);
      }
    } catch (error) {
      console.warn(`Error synchronizing initialValue for localStorage key “${key}”:`, error);
    }
  }, [key, initialValue]);

  return [storedValue, setValue];
};

export default useLocalStorage;

// Example Usage:
// function UserNameInput() {
//   const [name, setName] = useLocalStorage('userName', 'Guest');
//
//   return (
//     <div>
//       <input
//         type="text"
//         value={name}
//         onChange={(e) => setName(e.target.value)}
//         placeholder="Enter your name"
//       />
//       <p>Hello, {name}!</p>
//     </div>
//   );
// }