useasyncbatcher.md

id	useAsyncBatcher
title	useAsyncBatcher

Function: useAsyncBatcher()

function useAsyncBatcher<TValue, TResult, TSelected>(
   fn, 
   options, 
selector): ReactAsyncBatcher<TValue, TResult, TSelected>

Defined in: react-pacer/src/async-batcher/useAsyncBatcher.ts:167

A React hook that creates an AsyncBatcher instance for managing asynchronous batches of items.

This is the async version of the useBatcher hook. Unlike the sync version, this async batcher:

• Handles promises and returns results from batch executions
• Provides error handling with configurable error behavior
• Tracks success, error, and settle counts separately
• Has state tracking for when batches are executing
• Returns the result of the batch function execution

Features:

• Configurable batch size and wait time
• Custom batch processing logic via getShouldExecute
• Event callbacks for monitoring batch operations
• Error handling for failed batch operations
• Automatic or manual batch processing

The batcher collects items and processes them in batches based on:

• Maximum batch size (number of items per batch)
• Time-based batching (process after X milliseconds)
• Custom batch processing logic via getShouldExecute

Error Handling:

• If an onError handler is provided, it will be called with the error and batcher instance
• If throwOnError is true (default when no onError handler is provided), the error will be thrown
• If throwOnError is false (default when onError handler is provided), the error will be swallowed
• Both onError and throwOnError can be used together - the handler will be called before any error is thrown
• The error state can be checked using the underlying AsyncBatcher instance

State Management and Selector

The hook uses TanStack Store for reactive state management. The selector parameter allows you to specify which state changes will trigger a re-render, optimizing performance by preventing unnecessary re-renders when irrelevant state changes occur.

By default, there will be no reactive state subscriptions and you must opt-in to state tracking by providing a selector function. This prevents unnecessary re-renders and gives you full control over when your component updates. Only when you provide a selector will the component re-render when the selected state values change.

Available state properties:

• errorCount: Number of batch executions that have resulted in errors
• failedItems: Array of items that failed during batch processing
• isEmpty: Whether the batcher has no items to process
• isExecuting: Whether a batch is currently being processed asynchronously
• isPending: Whether the batcher is waiting for the timeout to trigger batch processing
• isRunning: Whether the batcher is active and will process items automatically
• items: Array of items currently queued for batch processing
• lastResult: The result from the most recent batch execution
• settleCount: Number of batch executions that have completed (success or error)
• size: Number of items currently in the batch queue
• status: Current processing status ('idle' | 'pending' | 'executing' | 'populated')
• successCount: Number of batch executions that have completed successfully
• totalItemsProcessed: Total number of items processed across all batches
• totalItemsFailed: Total number of items that have failed processing

Type Parameters

• TValue

• TResult

• TSelected = {}

Parameters

fn

(items) => Promise<TResult>

options

AsyncBatcherOptions<TValue, TResult> = {}

selector

(state) => TSelected

Returns

ReactAsyncBatcher<TValue, TResult, TSelected>

Example

// Basic async batcher for API requests - no reactive state subscriptions
const asyncBatcher = useAsyncBatcher(
  async (items: Item[]) => {
    const results = await Promise.all(items.map(item => processItem(item)));
    return results;
  },
  { maxSize: 10, wait: 2000 }
);

// Opt-in to re-render when execution state changes (optimized for loading indicators)
const asyncBatcher = useAsyncBatcher(
  async (items: Item[]) => {
    const results = await Promise.all(items.map(item => processItem(item)));
    return results;
  },
  { maxSize: 10, wait: 2000 },
  (state) => ({
    isExecuting: state.isExecuting,
    isPending: state.isPending,
    status: state.status
  })
);

// Opt-in to re-render when results are available (optimized for data display)
const asyncBatcher = useAsyncBatcher(
  async (items: Item[]) => {
    const results = await Promise.all(items.map(item => processItem(item)));
    return results;
  },
  { maxSize: 10, wait: 2000 },
  (state) => ({
    lastResult: state.lastResult,
    successCount: state.successCount,
    totalItemsProcessed: state.totalItemsProcessed
  })
);

// Opt-in to re-render when error state changes (optimized for error handling)
const asyncBatcher = useAsyncBatcher(
  async (items: Item[]) => {
    const results = await Promise.all(items.map(item => processItem(item)));
    return results;
  },
  {
    maxSize: 10,
    wait: 2000,
    onError: (error) => console.error('Batch processing failed:', error)
  },
  (state) => ({
    errorCount: state.errorCount,
    failedItems: state.failedItems,
    totalItemsFailed: state.totalItemsFailed
  })
);

// Complete example with all callbacks
const asyncBatcher = useAsyncBatcher(
  async (items: Item[]) => {
    const results = await Promise.all(items.map(item => processItem(item)));
    return results;
  },
  {
    maxSize: 10,
    wait: 2000,
    onSuccess: (result) => {
      console.log('Batch processed successfully:', result);
    },
    onError: (error) => {
      console.error('Batch processing failed:', error);
    }
  }
);

// Add items to batch
asyncBatcher.addItem(newItem);

// Manually execute batch
const result = await asyncBatcher.execute();

// Access the selected state (will be empty object {} unless selector provided)
const { isExecuting, lastResult, size } = asyncBatcher.state;