SWR and React Query libraries in React

SWR and React Query are two popular libraries for data fetching and state management in React applications. Both libraries aim to simplify data fetching, caching, and synchronization, but they have different design philosophies and features. Here's a detailed comparison of SWR and React Query:

SWR (Stale-While-Revalidate)

SWR stands for "Stale-While-Revalidate," a cache invalidation strategy where stale data is served while a new version is fetched and then replaces the stale data.

Key Features

1. Stale-While-Revalidate:

   • Returns cached data (stale) while fetching new data (revalidate).

2. Automatic Revalidation:

   • Automatically revalidates and updates data on re-fetching, focus, and network reconnect.

3. Simple API:

   • Provides a minimalistic and intuitive API for data fetching.

4. Built-In Caching:

   • In-memory caching with configurable cache providers.

5. Focus and Reconnect:

   • Automatically refetches data when the window is refocused or the network reconnects.

6. Supports fetch API:

   • Built around the fetch API but can be extended to use other data-fetching methods.

Example

import useSWR from 'swr';

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

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

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

  return <div>User: {data.name}</div>;
}

React Query

React Query is a library for managing server state in React applications, offering more advanced features and flexibility than SWR.

Key Features

1. Rich API:

   • Provides a comprehensive API for data fetching, caching, synchronization, and updates.

2. Query and Mutation:

   • Supports both queries (data fetching) and mutations (data modification).

3. Query Invalidation:

   • Allows manual invalidation and refetching of queries.

4. Background Fetching:

   • Fetches data in the background to keep data fresh.

5. Automatic Refetching:

   • Configurable options for automatic refetching on focus, network reconnect, or intervals.

6. DevTools:

   • Includes a set of DevTools for inspecting and debugging queries.

7. Optimistic Updates:

   • Supports optimistic updates for better user experience during mutations.

8. Pagination and Infinite Query:

   • Built-in support for pagination and infinite scrolling.

Example

import { useQuery } from 'react-query';

// Fetcher function
const fetchUser = async () => {
  const response = await fetch('/api/user');
  if (!response.ok) throw new Error('Network error');
  return response.json();
};

function UserProfile() {
  const { data, error, isLoading } = useQuery('user', fetchUser);

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

  return <div>User: {data.name}</div>;
}

Comparison

1. API and Complexity

• SWR: Minimalistic and straightforward API with a focus on simplicity. Ideal for basic use cases and projects where minimal configuration is preferred.
• React Query: More complex but feature-rich API. Provides advanced capabilities like query invalidation, mutations, pagination, and DevTools support.

2. Caching and Data Management

• SWR: In-memory caching with a simple and intuitive approach. Best for applications with simpler caching needs.
• React Query: Advanced caching mechanisms with options for background fetching, automatic refetching, and query invalidation.

3. Automatic Refetching

• SWR: Refetches data on focus, network reconnect, and interval (configurable).
• React Query: Configurable options for refetching on focus, network reconnect, and intervals. More flexibility and control over refetching behavior.

4. Mutations

• SWR: Primarily focused on data fetching. Supports simple mutation handling but lacks advanced features.
• React Query: Full support for mutations, including optimistic updates and error handling.

5. DevTools

• SWR: No built-in DevTools.
• React Query: Includes a set of DevTools for inspecting and debugging queries.

6. Pagination and Infinite Queries

• SWR: No built-in support for pagination or infinite queries.
• React Query: Provides built-in support for pagination and infinite scrolling.

When to Use Each

• Use SWR if you prefer a simple, lightweight library with minimal configuration and your data-fetching needs are relatively straightforward.
• Use React Query if you need advanced features like query invalidation, mutation support, pagination, and DevTools, or if your application requires more control and flexibility in managing server state.