📄 tanstack/pacer/latest/docs/framework/react/examples/useAsyncQueuer

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tsx

import { useState } from 'react'
import ReactDOM from 'react-dom/client'
import { useAsyncQueuer } from '@tanstack/react-pacer/async-queuer'
import { PacerProvider } from '@tanstack/react-pacer/provider'

const fakeWaitTime = 500

type Item = number

function App() {
  const [concurrency, setConcurrency] = useState(2)

  // The function to process each item (now a number)
  async function processItem(item: Item): Promise<void> {
    await new Promise((resolve) => setTimeout(resolve, fakeWaitTime))
    console.log(`Processed ${item}`)
  }

  const asyncQueuer = useAsyncQueuer(
    processItem, // your function to queue/process items
    {
      maxSize: 25,
      initialItems: Array.from({ length: 10 }, (_, i) => i + 1),
      concurrency, // Process 2 items concurrently
      started: false,
      wait: 100, // for demo purposes - usually you would not want extra wait time if you are also throttling with concurrency
      onReject: (item, asyncQueuer) => {
        console.log(
          'Queue is full, rejecting item',
          item,
          asyncQueuer.store.state.rejectionCount,
        )
      },
      onError: (error, item: Item, asyncQueuer) => {
        console.error(
          `Error processing item: ${item}`,
          error,
          asyncQueuer.store.state.errorCount,
        ) // optionally, handle errors here instead of your own try/catch
      },
    },
    // Optional Selector function to pick the state you want to track and use
    (state) => ({
      size: state.size,
      isFull: state.isFull,
      isEmpty: state.isEmpty,
      isIdle: state.isIdle,
      status: state.status,
      successCount: state.successCount,
      rejectionCount: state.rejectionCount,
      activeItems: state.activeItems,
      items: state.items,
      isRunning: state.isRunning,
    }),
  )

  return (
    <div>
      <h1>TanStack Pacer useAsyncQueuer Example</h1>
      <div></div>
      <div>Queue Size: {asyncQueuer.state.size}</div>
      <div>Queue Max Size: {25}</div>
      <div>Queue Full: {asyncQueuer.state.isFull ? 'Yes' : 'No'}</div>
      <div>Queue Empty: {asyncQueuer.state.isEmpty ? 'Yes' : 'No'}</div>
      <div>Queue Idle: {asyncQueuer.state.isIdle ? 'Yes' : 'No'}</div>
      <div>Queuer Status: {asyncQueuer.state.status}</div>
      <div>Items Processed: {asyncQueuer.state.successCount}</div>
      <div>Items Rejected: {asyncQueuer.state.rejectionCount}</div>
      <div>Active Tasks: {asyncQueuer.state.activeItems.length}</div>
      <div>Pending Tasks: {asyncQueuer.state.items.length}</div>
      <div>
        Concurrency:{' '}
        <input
          type="number"
          min={1}
          value={concurrency}
          onChange={(e) =>
            setConcurrency(Math.max(1, parseInt(e.target.value) || 1))
          }
          style={{ width: '60px' }}
        />
      </div>
      <div style={{ minHeight: '250px' }}>
        Queue Items:
        {asyncQueuer.peekAllItems().map((item, index) => (
          <div key={index}>
            {index}: {item}
          </div>
        ))}
      </div>
      <div
        style={{
          display: 'grid',
          gridTemplateColumns: 'repeat(2, 1fr)',
          gap: '8px',
          maxWidth: '600px',
          margin: '16px 0',
        }}
      >
        <button
          onClick={() => {
            const nextNumber = asyncQueuer.peekAllItems().length
              ? Math.max(...asyncQueuer.peekAllItems()) + 1
              : 1
            asyncQueuer.addItem(nextNumber)
          }}
          disabled={asyncQueuer.state.isFull}
        >
          Add Async Task
        </button>
        <button onClick={() => asyncQueuer.getNextItem()}>Get Next Item</button>
        <button
          onClick={() => asyncQueuer.clear()}
          disabled={asyncQueuer.state.isEmpty}
        >
          Clear Queue
        </button>
        <button
          onClick={() => asyncQueuer.flush()}
          disabled={asyncQueuer.state.isEmpty}
        >
          Flush Queue
        </button>
        <button
          onClick={() => asyncQueuer.start()}
          disabled={asyncQueuer.state.isRunning}
        >
          Start Processing
        </button>
        <button
          onClick={() => asyncQueuer.stop()}
          disabled={!asyncQueuer.state.isRunning}
        >
          Stop Processing
        </button>
        <button onClick={() => asyncQueuer.reset()}>Reset Queue</button>
      </div>
      <pre style={{ marginTop: '20px' }}>
        {JSON.stringify(asyncQueuer.store.state, null, 2)}
      </pre>
    </div>
  )
}

const root = ReactDOM.createRoot(document.getElementById('root')!)
root.render(
  // optionally, provide default options to an optional PacerProvider
  <PacerProvider
  // defaultOptions={{
  //   queuer: {
  //     maxSize: 50,
  //   },
  // }}
  >
    <App />
  </PacerProvider>,
)


import { useState } from 'react'
import ReactDOM from 'react-dom/client'
import { useAsyncQueuer } from '@tanstack/react-pacer/async-queuer'
import { PacerProvider } from '@tanstack/react-pacer/provider'

const fakeWaitTime = 500

type Item = number

function App() {
  const [concurrency, setConcurrency] = useState(2)

  // The function to process each item (now a number)
  async function processItem(item: Item): Promise<void> {
    await new Promise((resolve) => setTimeout(resolve, fakeWaitTime))
    console.log(`Processed ${item}`)
  }

  const asyncQueuer = useAsyncQueuer(
    processItem, // your function to queue/process items
    {
      maxSize: 25,
      initialItems: Array.from({ length: 10 }, (_, i) => i + 1),
      concurrency, // Process 2 items concurrently
      started: false,
      wait: 100, // for demo purposes - usually you would not want extra wait time if you are also throttling with concurrency
      onReject: (item, asyncQueuer) => {
        console.log(
          'Queue is full, rejecting item',
          item,
          asyncQueuer.store.state.rejectionCount,
        )
      },
      onError: (error, item: Item, asyncQueuer) => {
        console.error(
          `Error processing item: ${item}`,
          error,
          asyncQueuer.store.state.errorCount,
        ) // optionally, handle errors here instead of your own try/catch
      },
    },
    // Optional Selector function to pick the state you want to track and use
    (state) => ({
      size: state.size,
      isFull: state.isFull,
      isEmpty: state.isEmpty,
      isIdle: state.isIdle,
      status: state.status,
      successCount: state.successCount,
      rejectionCount: state.rejectionCount,
      activeItems: state.activeItems,
      items: state.items,
      isRunning: state.isRunning,
    }),
  )

  return (
    <div>
      <h1>TanStack Pacer useAsyncQueuer Example</h1>
      <div></div>
      <div>Queue Size: {asyncQueuer.state.size}</div>
      <div>Queue Max Size: {25}</div>
      <div>Queue Full: {asyncQueuer.state.isFull ? 'Yes' : 'No'}</div>
      <div>Queue Empty: {asyncQueuer.state.isEmpty ? 'Yes' : 'No'}</div>
      <div>Queue Idle: {asyncQueuer.state.isIdle ? 'Yes' : 'No'}</div>
      <div>Queuer Status: {asyncQueuer.state.status}</div>
      <div>Items Processed: {asyncQueuer.state.successCount}</div>
      <div>Items Rejected: {asyncQueuer.state.rejectionCount}</div>
      <div>Active Tasks: {asyncQueuer.state.activeItems.length}</div>
      <div>Pending Tasks: {asyncQueuer.state.items.length}</div>
      <div>
        Concurrency:{' '}
        <input
          type="number"
          min={1}
          value={concurrency}
          onChange={(e) =>
            setConcurrency(Math.max(1, parseInt(e.target.value) || 1))
          }
          style={{ width: '60px' }}
        />
      </div>
      <div style={{ minHeight: '250px' }}>
        Queue Items:
        {asyncQueuer.peekAllItems().map((item, index) => (
          <div key={index}>
            {index}: {item}
          </div>
        ))}
      </div>
      <div
        style={{
          display: 'grid',
          gridTemplateColumns: 'repeat(2, 1fr)',
          gap: '8px',
          maxWidth: '600px',
          margin: '16px 0',
        }}
      >
        <button
          onClick={() => {
            const nextNumber = asyncQueuer.peekAllItems().length
              ? Math.max(...asyncQueuer.peekAllItems()) + 1
              : 1
            asyncQueuer.addItem(nextNumber)
          }}
          disabled={asyncQueuer.state.isFull}
        >
          Add Async Task
        </button>
        <button onClick={() => asyncQueuer.getNextItem()}>Get Next Item</button>
        <button
          onClick={() => asyncQueuer.clear()}
          disabled={asyncQueuer.state.isEmpty}
        >
          Clear Queue
        </button>
        <button
          onClick={() => asyncQueuer.flush()}
          disabled={asyncQueuer.state.isEmpty}
        >
          Flush Queue
        </button>
        <button
          onClick={() => asyncQueuer.start()}
          disabled={asyncQueuer.state.isRunning}
        >
          Start Processing
        </button>
        <button
          onClick={() => asyncQueuer.stop()}
          disabled={!asyncQueuer.state.isRunning}
        >
          Stop Processing
        </button>
        <button onClick={() => asyncQueuer.reset()}>Reset Queue</button>
      </div>
      <pre style={{ marginTop: '20px' }}>
        {JSON.stringify(asyncQueuer.store.state, null, 2)}
      </pre>
    </div>
  )
}

const root = ReactDOM.createRoot(document.getElementById('root')!)
root.render(
  // optionally, provide default options to an optional PacerProvider
  <PacerProvider
  // defaultOptions={{
  //   queuer: {
  //     maxSize: 50,
  //   },
  // }}
  >
    <App />
  </PacerProvider>,
)

useQueuedValue

useAsyncQueuedState

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