Source URL: https://tanstack.com/query/latest/docs/framework/react/examples/basic

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React Example: Basic

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public
src
- index.tsx
.gitignore
README.md
eslint.config.js
index.html
package.json
tsconfig.json
vite.config.ts

tsx

    import * as React from 'react'
    import ReactDOM from 'react-dom/client'
    import { QueryClient, useQuery, useQueryClient } from '@tanstack/react-query'
    import { PersistQueryClientProvider } from '@tanstack/react-query-persist-client'
    import { createAsyncStoragePersister } from '@tanstack/query-async-storage-persister'
    import { ReactQueryDevtools } from '@tanstack/react-query-devtools'

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

    const persister = createAsyncStoragePersister({
      storage: window.localStorage,
    })

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

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

      return (
          <h1>Posts</h1>
            {status === 'pending' ? (
              'Loading...'
            ) : status === 'error' ? (
              <span>Error: {error.message}</span>
            ) : (
              <>
                  {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>{isFetching ? 'Background Updating...' : ' '}</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 (
            <a onClick={() => setPostId(-1)} href="#">
              Back
            </a>
          {!postId || status === 'pending' ? (
            'Loading...'
          ) : status === 'error' ? (
            <span>Error: {error.message}</span>
          ) : (
            <>
              <h1>{data.title}</h1>
                <p>{data.body}</p>
              <div>{isFetching ? 'Background Updating...' : ' '}</div>
            </>
          )}
      )
    }

    function App() {
      const [postId, setPostId] = React.useState(-1)

      return (
          <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 ? (
          ) : (
          )}
      )
    }

    const rootElement = document.getElementById('root') as HTMLElement
    ReactDOM.createRoot(rootElement).render(<App />)

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