React Query is a powerful data management library that simplifies data fetching, caching, and updating in React applications. With its simple, declarative API and support for complex data scenarios like pagination and optimistic updates, React Query is a great choice for any React developer looking to streamline their data management code.

One of the key benefits of React Query is its ability to cache data and automatically handle stale data. This means that if a component needs to render data that has already been fetched, React Query will return the cached data rather than making a new network request.

Additionally, React Query includes a number of features that make it easy to manage complex data fetching scenarios, such as pagination, optimistic updates, and polling.

Now that we've covered the basics, let's dive into some of the key features of React Query

-- Querying Data:
At its core, React Query is all about fetching and managing data. To fetch data, you can use the useQuery hook, which takes a query key and an async function that returns the data you want to fetch. Here's an example:

import { useQuery } from 'react-query'

function MyComponent() {
  const { isLoading, data } = useQuery('todos', async () => {
    const response = await fetch('/api/todos')
    return response.json()
  })

  if (isLoading) return <div>Loading...</div>

  return (
    <ul>
      {data.map(todo => (
        <li key={todo.id}>{todo.title}</li>
      ))}
    </ul>
  )
}

In this example, we're fetching a list of todos from an API and rendering them in a list. The useQuery hook takes a string key ('todos') that is used to cache the results, as well as an async function that fetches the data.

-- Mutating Data:
In addition to fetching data, React Query also provides a way to mutate data using the useMutation hook. This hook takes a mutation function that performs the update on the server, and returns an object with a mutate function that you can call to trigger the mutation.

import { useMutation, useQueryClient } from 'react-query'

function AddTodo() {
  const queryClient = useQueryClient()

  const { mutate, isLoading } = useMutation(
    async (todo) => {
      const response = await fetch('/api/todos', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify(todo)
      })
      return response.json()
    },
    {
      onSuccess: () => {
        queryClient.invalidateQueries('todos')
      }
    }
  )

  const handleSubmit = async (e) => {
    e.preventDefault()
    const { value } = e.target.elements.title
    mutate({ title: value })
  }

  return (
    <form onSubmit={handleSubmit}>
      <input type="text" name="title" />
      <button type="submit" disabled={isLoading}>
        {isLoading ? 'Adding...' : 'Add'}
      </button>
    </form>
  )
}

In this example, we're using the useMutation hook to add a new todo to the server. The mutate function takes an object with the data to be added, and automatically updates the cache with the new data when the mutation is successful.

--Paginating Data:
Another common scenario in data fetching is pagination. React Query makes it easy to implement pagination using the useInfiniteQuery hook, which allows you to fetch data in chunks and add them to the cache as they are loaded.

import { useInfiniteQuery } from 'react-query'

function MyComponent() {
  const { data, error, fetchNextPage, hasNextPage, isFetching } = useInfiniteQuery(
    'todos',
    ({ pageParam = 0 }) => fetch(`/api/todos?page=${pageParam}`).then(res => res.json()),
    {
      getNextPageParam: (lastPage) => lastPage.nextPage,
    }
  )

  if (error) return <div>Error fetching data</div>

  return (
    <>
      {data.pages.map(page => (
        <ul key={page.pageNumber}>
          {page.todos.map(todo => (
            <li key={todo.id}>{todo.title}</li>
          ))}
        </ul>
      ))}

      <button onClick={() => fetchNextPage()} disabled={!hasNextPage || isFetching}>
        {isFetching ? 'Loading more...' : hasNextPage ? 'Load More' : 'Nothing more to load'}
      </button>
    </>
  )
}

In this example, we're using the useInfiniteQuery hook to fetch todos in pages from an API. The fetchNextPage function is used to load the next page of todos, and the hasNextPage property is used to disable the "Load More" button when there are no more pages to fetch.

The getNextPageParam function is used to return the nextPage value from the last page of data, which is used to fetch the next page of data.

If you want to learn more about React Query, there are many resources available online. One great place to start is the official React Query documentation, which provides detailed information on how to use the library.
Official Documentation Link:
Here is the official documentation of the library.

Additionally, there are many excellent YouTube tutorials available that cover React Query in-depth. One such channel is Code Evolution, which has a comprehensive React Query tutorial series that covers everything from basic usage to advanced topics like pagination and optimistic updates. Here is the playlist link that I have followed and it's great if you ask me.
Youtube playlist that I have followed

If you want to see React Query in action, you can check out a sample project that uses the library. I have created a GitHub repo that contains a simple React application that fetches data from an API using React Query. The project also demonstrates how to implement pagination using the useInfiniteQuery hook. Here is the repo link that I have created.
The project repo
I have followed the youtube tutorial link that I have given here.

In conclusion, React Query is a powerful and flexible library that makes it easy to manage data in React applications. Whether you're a beginner or an experienced developer, React Query is definitely worth checking out!