React Query Basics

React Query is a powerful data fetching and caching library for React applications. It simplifies the process of managing server-state, providing features like caching, retrying, and optimistic updates out of the box. With React Query, you can focus on building your application’s core features while it handles the complexities of data fetching.

Basic Example

To get started with React Query, you’ll need to install it using npm or yarn. Once installed, you can set up the Query Client and Query Client Provider in your application. Here’s a simple example:

// Import necessary components
import { QueryClient, QueryClientProvider, useQuery } from '@tanstack/react-query';
 
// Create a Query Client
const queryClient = new QueryClient();
 
// Create a function to fetch data
const fetchData = async () => {
  const response = await fetch('https://jsonplaceholder.typicode.com/posts');
  return response.json();
};
 
// Use the useQuery hook to fetch data
function Posts() {
  const { data, error, isLoading } = useQuery(['posts'], fetchData);
 
  if (isLoading) return <div>Loading...</div>;
  if (error) return <div>Error: {error.message}</div>;
 
  return (
    <div>
      {data.map((post) => (
        <div key={post.id}>{post.title}</div>
      ))}
    </div>
  );
}
 
// Wrap your application with the Query Client Provider
function App() {
  return (
    <QueryClientProvider client={queryClient}>
      <Posts />
    </QueryClientProvider>
  );
}

In this example, we create a Query Client and a function to fetch data from a JSON placeholder API. We then use the useQuery hook to fetch the data and display it in our component.

Advanced Usage

For more complex scenarios, you can use React Query’s features like pagination, caching, and retrying. Here’s an example of how to use pagination:

// Create a function to fetch paginated data
const fetchPosts = async ({ queryKey }) => {
  const page = queryKey[1];
  const response = await fetch(`https://jsonplaceholder.typicode.com/posts?_page=${page}`);
  return response.json();
};
 
// Use the useQuery hook with pagination
function Posts() {
  const [page, setPage] = useState(1);
  const { data, error, isLoading, isFetching } = useQuery(['posts', page], fetchPosts);
 
  if (isLoading) return <div>Loading...</div>;
  if (error) return <div>Error: {error.message}</div>;
 
  return (
    <div>
      {data.map((post) => (
        <div key={post.id}>{post.title}</div>
      ))}
      <button onClick={() => setPage(page + 1)}>Next Page</button>
      {isFetching ? <div>Fetching...</div> : null}
    </div>
  );
}

In this example, we create a function to fetch paginated data and use the useQuery hook with pagination. We also use the isFetching state to display a “Fetching…” message while the data is being fetched.

Best Practices

Here are some best practices to keep in mind when using React Query:

• Always use the QueryClientProvider to wrap your application and provide the Query Client to your components.
• Use the useQuery hook to fetch data and display it in your components.
• Use the useMutation hook to perform mutations and update the data in your components.
• Always handle errors and loading states in your components to provide a good user experience.

Key Takeaways

Here are the key takeaways from this guide:

• React Query is a powerful data fetching and caching library for React applications.
• Use the QueryClientProvider to wrap your application and provide the Query Client to your components.
• Use the useQuery hook to fetch data and display it in your components.
• Always handle errors and loading states in your components to provide a good user experience.