index.tsx

import { createRoot } from 'react-dom/client'
import {
  QueryClient,
  QueryClientProvider,
  useQuery,
  useQueryClient,
} from '@tanstack/react-query'
import { useState } from 'react'
import Devtools from './setup'

const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      gcTime: 1000 * 60 * 60 * 24, // 24 hours
    },
  },
})

type Post = {
  id: number
  title: string
  body: string
}

function Posts({
  setPostId,
}: {
  setPostId: React.Dispatch<React.SetStateAction<number>>
}) {
  const queryClient = useQueryClient()
  const { status, data, error, isFetching } = usePosts()

  return (
    <div>
      <h1>Posts</h1>
      <div>
        {status === 'pending' ? (
          'Loading...'
        ) : status === 'error' ? (
          <span>Error: {error.message}</span>
        ) : (
          <>
            <div>
              {data.map((post) => (
                <p key={post.id}>
                  <a
                    onClick={() => setPostId(post.id)}
                    href="#"
                    style={
                      // We can access the query data here to show bold links for
                      // ones that are cached
                      queryClient.getQueryData(['post', post.id])
                        ? {
                            fontWeight: 'bold',
                            color: 'green',
                          }
                        : {}
                    }
                  >
                    {post.title}
                  </a>
                </p>
              ))}
            </div>
            <div>{isFetching ? 'Background Updating...' : ' '}</div>
          </>
        )}
      </div>
    </div>
  )
}

const getPostById = async (id: number): Promise<Post> => {
  const response = await fetch(
    `https://jsonplaceholder.typicode.com/posts/${id}`,
  )
  return await response.json()
}

function usePost(postId: number) {
  return useQuery({
    queryKey: ['post', postId],
    queryFn: () => getPostById(postId),
    enabled: !!postId,
  })
}

function Post({
  postId,
  setPostId,
}: {
  postId: number
  setPostId: React.Dispatch<React.SetStateAction<number>>
}) {
  const { status, data, error, isFetching } = usePost(postId)

  return (
    <div>
      <div>
        <a onClick={() => setPostId(-1)} href="#">
          Back
        </a>
      </div>
      {!postId || status === 'pending' ? (
        'Loading...'
      ) : status === 'error' ? (
        <span>Error: {error.message}</span>
      ) : (
        <>
          <h1>{data.title}</h1>
          <div>
            <p>{data.body}</p>
          </div>
          <div>{isFetching ? 'Background Updating...' : ' '}</div>
        </>
      )}
    </div>
  )
}
function usePosts() {
  return useQuery({
    queryKey: ['posts'],
    queryFn: async (): Promise<Array<Post>> => {
      const response = await fetch('https://jsonplaceholder.typicode.com/posts')
      return await response.json()
    },
  })
}
function App() {
  const [postId, setPostId] = useState(-1)

  return (
    <div>
      <QueryClientProvider client={queryClient}>
        <p>
          As you visit the posts below, you will notice them in a loading state
          the first time you load them. However, after you return to this list
          and click on any posts you have already visited again, you will see
          them load instantly and background refresh right before your eyes!{' '}
          <strong>
            (You may need to throttle your network speed to simulate longer
            loading sequences)
          </strong>
        </p>
        {postId > -1 ? (
          <Post postId={postId} setPostId={setPostId} />
        ) : (
          <Posts setPostId={setPostId} />
        )}
        <Devtools />
      </QueryClientProvider>
      <h1>TanStack Devtools React Basic Example</h1>
    </div>
  )
}

const root = createRoot(document.getElementById('root')!)
root.render(<App />)