How to use localStorage in Next.js | Updated 2024

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Next.js is a popular React framework that enables server-side rendering and static site generation. However, handling client-side features like localStorage requires careful consideration due to the differences between server-side and client-side execution. This guide will walk you through how to use localStorage in a Next.js application effectively.

Steps for usage of localStorage in Next.js

Step 1: Setting Up Your Next.js Project

First, create a new Next.js project if you don’t have one already:

npx create-next-app@latest my-nextjs-app
cd my-nextjs-app

Start the development server:

npm run dev

Step 2: Understanding Server-Side and Client-Side Rendering

Next.js renders pages on the server by default, but localStorage is a browser-specific feature, meaning it is only available on the client-side. Thus, any code accessing localStorage must only run on the client.

Step 3: Using localStorage in a Next.js Component

To safely access localStorage, you need to ensure the code runs only on the client side. This can be done using React hooks like useEffect.

// pages/index.js

import { useState, useEffect } from 'react';

const Home = () => {
  const [name, setName] = useState('');

  useEffect(() => {
    // Check if the window object is available
    if (typeof window !== 'undefined') {
      // Retrieve the name from localStorage
      const storedName = localStorage.getItem('name');
      if (storedName) {
        setName(storedName);
      }
    }
  }, []);

  const handleChange = (e) => {
    setName(e.target.value);
    localStorage.setItem('name', e.target.value);
  };

  return (
    <div>
      <h1>Welcome, {name}</h1>
      <input type="text" value={name} onChange={handleChange} placeholder="Enter your name" />
    </div>
  );
};

export default Home;

Explanation

useEffect

This hook ensures the code inside it runs only after the component has mounted, which is exclusively on the client side.

typeof window !== ‘undefined’

This check ensures that the code accessing localStorage only runs in a browser environment where window is defined.

Step 4: Handling SSR with localStorage

In cases where you need to handle server-side rendering (SSR) with Next.js and still want to access localStorage, you should always ensure your localStorage code is protected by client-side checks.

Advanced Usage: Custom Hook for localStorage

To avoid repetitive code and handle localStorage more elegantly, you can create a custom hook.

// hooks/useLocalStorage.js

import { useState, useEffect } from 'react';

const useLocalStorage = (key, initialValue) => {
  const [storedValue, setStoredValue] = useState(() => {
    if (typeof window === 'undefined') return initialValue;

    try {
      const item = window.localStorage.getItem(key);
      return item ? JSON.parse(item) : initialValue;
    } catch (error) {
      console.error(error);
      return initialValue;
    }
  });

  const setValue = (value) => {
    try {
      const valueToStore = value instanceof Function ? value(storedValue) : value;
      setStoredValue(valueToStore);
      if (typeof window !== 'undefined') {
        window.localStorage.setItem(key, JSON.stringify(valueToStore));
      }
    } catch (error) {
      console.error(error);
    }
  };

  return [storedValue, setValue];
};

export default useLocalStorage;

Using the Custom Hook

// pages/index.js

import useLocalStorage from '../hooks/useLocalStorage';

const Home = () => {
  const [name, setName] = useLocalStorage('name', '');

  return (
    <div>
      <h1>Welcome, {name}</h1>
      <input type="text" value={name} onChange={(e) => setName(e.target.value)} placeholder="Enter your name" />
    </div>
  );
};

export default Home;

Conclusion

By following these steps, you can effectively manage state with localStorage in your Next.js application. Remember to always check for the client environment when dealing with browser-specific features to avoid errors during server-side rendering. Using custom hooks like useLocalStorage can also help encapsulate and manage localStorage logic more cleanly and efficiently.

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How to use localStorage in Next.js – FAQs