JAVASCRIPT
Persist React State with `useLocalStorage` Custom Hook
A reusable React hook to store and retrieve state from browser's localStorage, maintaining data across page refreshes for user preferences or forms.
import { useState, useEffect } from 'react';
function useLocalStorage(key, initialValue) {
// State to store our value
// Pass initial state function to useState so logic is only executed once
const [storedValue, setStoredValue] = useState(() => {
try {
const item = window.localStorage.getItem(key);
return item ? JSON.parse(item) : initialValue;
} catch (error) {
console.error(error);
return initialValue;
}
});
// useEffect to update local storage when the state changes
useEffect(() => {
try {
window.localStorage.setItem(key, JSON.stringify(storedValue));
} catch (error) {
console.error(error);
}
}, [key, storedValue]);
return [storedValue, setStoredValue];
}
// How to use it:
// function ThemeToggler() {
// const [theme, setTheme] = useLocalStorage('appTheme', 'light');
// const toggleTheme = () => {
// setTheme(theme === 'light' ? 'dark' : 'light');
// };
// return (
// <button onClick={toggleTheme}>
// Switch to {theme === 'light' ? 'dark' : 'light'} Theme
// </button>
// );
// }
How it works: This custom hook synchronizes a React state variable with an entry in the browser's `localStorage`. It initializes the state by attempting to retrieve a value from `localStorage` or falling back to a provided initial value. An `useEffect` hook ensures that whenever the state changes, the new value is automatically saved to `localStorage`, making the state persistent across sessions and page refreshes.