In this chapter, you will learn about an important tool that React developers use for data fetching and state management. At the end of this chapter, we'll explore its core concepts, delve into practical examples, and uncover advanced techniques to supercharge your React development workflow.

What is React Query?

React Query is a powerful data fetching and state management library that simplifies how you work with asynchronous data in your React applications. It eliminates the need for verbose and complex code often associated with traditional data fetching methods, allowing you to focus on building exceptional user experiences.

Why is React Query Important?

While React provides a robust component model for building user interfaces, handling asynchronous operations like data fetching can quickly introduce complexity into your applications.

You've likely encountered the following challenges:

• Repetitive Code: Writing data fetching logic within useEffect hooks repeatedly across different components leads to code duplication and maintainability issues.
• Cumbersome State Management: Manually tracking loading states, errors, and cached data introduces significant overhead and can make your components harder to reason about.
• Performance Bottlenecks: Without proper caching and request management, your application can suffer from slow loading times and unnecessary re-renders, impacting the user experience.

React Query addresses these pain points by providing a declarative and efficient approach to managing your asynchronous operations, leading to cleaner code, improved performance, and a more delightful developer experience.

The Problem with Traditional Data Fetching

In most React applications, we need to fetch data from an API. Traditionally, we use:

• The fetch API or Axios to make HTTP requests.
• React state (useState) to store the fetched data.
• Effect hooks (useEffect) to trigger API calls when the component mounts.

Let’s see an example:

import { useState, useEffect } from 'react';

const Users = () => {
  const [users, setUsers] = useState([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);

  useEffect(() => {
    fetch('https://jsonplaceholder.typicode.com/users')
      .then(response => response.json())
      .then(data => {
        setUsers(data);
        setLoading(false);
      })
      .catch(error => {
        setError(error);
        setLoading(false);
      });
  }, []);

  if (loading) return <p>Loading...</p>;
  if (error) return <p>Error: {error.message}</p>;

  return (
    <ul>
      {users.map(user => <li key={user.id}>{user.name}</li>)}
    </ul>
  );
};

Here are the issues with this approach:

• Redundant API Calls: Every time the component re-renders, it re-fetches data unless we manage caching manually.
• No Automatic Updates: If another component modifies the data, this component won’t reflect those changes unless we manually re-fetch.
• Difficult Error Handling: We must handle loading, error states, and retries ourselves.

How Does React Query Solve This

React Query automates data fetching and state management with:

• Built-in Caching: Prevents unnecessary API requests.
• Automatic Background Refetching: Keeps data fresh.
• Pagination and Infinite Scroll Support.
• Mutations with Optimistic Updates for a smooth UI experience.

In the next few lessons, you'll learn how to use React Query in your React projects to manage state and data fetching efficiently.