How to Use SWR: A Complete SWR Tutorial for React Applications

Efficient data fetching is crucial for modern web applications, and SWR (stale-while-revalidate) is one of the best libraries for managing remote data fetching in React. Developed by Vercel, SWR is designed to provide lightning-fast data fetching with caching, revalidation, and state management out of the box. In this SWR tutorial, we’ll walk you through how to use SWR in your React applications.

What is SWR?

SWR stands for stale-while-revalidate, a cache invalidation strategy. It ensures your app always shows stale data from the cache while revalidating and updating it in the background. This makes your app faster and more responsive, even with network latency.

Key Features of SWR:

• Data caching and revalidation.
• Built-in support for TypeScript.
• Lightweight and easy to integrate.
• Automatic retry on failure.
• Optimized for server-side rendering (SSR).

Why Use SWR in React Applications?

Are you tired of manually managing states, caching, and re-fetching data? SWR handles all this for you. It works seamlessly with React and provides:

• Better User Experience: Your app stays fast and responsive by displaying cached data instantly.
• Ease of Use: Minimal configuration required to get started.
• Flexibility: Integrates with any data-fetching method, such as fetch or axios.

Getting Started with SWR

Follow these steps to integrate SWR into your React application. This SWR tutorial is beginner-friendly and will help you understand the basics of how to use SWR effectively.

Step 1: Install SWR

Run the following command to install SWR in your React project:

npm install swr

Or, if you’re using Yarn:

yarn add swr

Step 2: Basic Usage

SWR uses the useSWR hook for data fetching. Here’s a simple example of fetching data from an API:

import useSWR from 'swr';

const fetcher = (url) => fetch(url).then((res) => res.json());

function App() {
  const { data, error, isLoading } = useSWR('/api/data', fetcher);

  if (isLoading) return <div>Loading...</div>;
  if (error) return <div>Error loading data</div>;

  return (
    <div>
      <h1>Data:</h1>
      <pre>{JSON.stringify(data, null, 2)}</pre>
    </div>
  );
}

export default App;

Explanation:

• useSWR(key, fetcher): The key is a unique identifier for the data being fetched, and the fetcher is a function that fetches the data.
• data: The response data from the API.
• error: Any error encountered during fetching.
• isLoading: A boolean indicating the loading state.

Advanced Usage of SWR

1. Handling Mutations

Use the mutate function to update data manually without refetching it:

import useSWR, { mutate } from 'swr';

function updateData() {
  mutate('/api/data', { key: 'new value' }, false); // Optimistic update
}

function App() {
  const { data } = useSWR('/api/data', fetcher);

  return (
    <div>
      <button onClick={updateData}>Update Data</button>
    </div>
  );
}

2. Pagination

SWR can handle paginated data using dynamic keys:

const fetcher = (url) => fetch(url).then((res) => res.json());

function PaginatedComponent({ page }) {
  const { data } = useSWR(`/api/data?page=${page}`, fetcher);

  return <div>{data ? data.items.join(', ') : 'Loading...'}</div>;
}

3. Revalidation Timing

Customize revalidation intervals:

useSWR('/api/data', fetcher, { refreshInterval: 5000 });

This will re-fetch the data every 5 seconds.

Tips for Using SWR Effectively

1. Error Handling: Use the error object to gracefully handle errors in your application.
2. TypeScript Integration: Define types for your fetched data to make your codebase robust.
3. Combine with SSR: Use SWR in server-rendered apps for pre-fetched data on the initial load.

Conclusion

SWR simplifies data fetching in React applications, offering powerful features like caching, revalidation, and error handling. Whether you’re building small projects or large-scale applications, SWR can help make your app faster and more reliable.

Ready to try SWR? Share your experience in the comments below, and don’t forget to subscribe for more React development tips. If this SWR tutorial was helpful, let us know how you’re using SWR in your projects!