Class: AsyncThrottler<TFn>

A class that creates an async throttled function.

Async vs Sync Versions: The async version provides advanced features over the sync Throttler:

Returns promises that can be awaited for throttled function results
Built-in retry support via AsyncRetryer integration
Abort support to cancel in-flight executions
Cancel support to prevent pending executions from starting
Comprehensive error handling with onError callbacks and throwOnError control
Detailed execution tracking (success/error/settle counts)
Waits for ongoing executions to complete before scheduling the next one
The sync Throttler is lighter weight and simpler when you don't need async features, return values, or execution control.
What is Throttling? Throttling limits how often a function can be executed, allowing only one execution within a specified time window. Unlike debouncing which resets the delay timer on each call, throttling ensures the function executes at a regular interval regardless of how often it's called.
This is useful for rate-limiting API calls, handling scroll/resize events, or any scenario where you want to ensure a maximum execution frequency.
Error Handling:
If an onError handler is provided, it will be called with the error and throttler 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 AsyncThrottler instance
State Management:
Uses TanStack Store for reactive state management
Use initialState to provide initial state values when creating the async throttler
Use onSuccess callback to react to successful function execution and implement custom logic
Use onError callback to react to function execution errors and implement custom error handling
Use onSettled callback to react to function execution completion (success or error) and implement custom logic
The state includes error count, execution status, last execution time, and success/settle counts
State can be accessed via asyncThrottler.store.state when using the class directly
When using framework adapters (React/Solid), state is accessed from asyncThrottler.state

Example

const throttler = new AsyncThrottler(async (value: string) => {
  const result = await saveToAPI(value);
  return result; // Return value is preserved
}, {
  wait: 1000,
  onError: (error) => {
    console.error('API call failed:', error);
  }
});

// Will only execute once per second no matter how often called
// Returns the API response directly
const result = await throttler.maybeExecute(inputElement.value);

Type Parameters

TFn

TFn extends AnyAsyncFunction

Constructors

Constructor

new AsyncThrottler<TFn>(fn, initialOptions): AsyncThrottler<TFn>;

Defined in: async-throttler.ts:242

Parameters

initialOptions

AsyncThrottlerOptions<TFn>

Returns

AsyncThrottler<TFn>

Properties

asyncRetryers

asyncRetryers: Map<number, AsyncRetryer<TFn>>;

Defined in: async-throttler.ts:236

key

key: string | undefined;

Defined in: async-throttler.ts:234

options

options: AsyncThrottlerOptions<TFn>;

Defined in: async-throttler.ts:235

store

readonly store: Store<Readonly<AsyncThrottlerState<TFn>>>;

Defined in: async-throttler.ts:231

Methods

abort()

abort(): void;

Defined in: async-throttler.ts:533

Aborts all ongoing executions with the internal abort controllers. Does NOT cancel any pending execution that have not started yet.

Returns

void

cancel()

cancel(): void;

Defined in: async-throttler.ts:543

Cancels any pending execution that have not started yet. Does NOT abort any execution already in progress.

Returns

void

flush()

flush(): Promise<ReturnType<TFn> | undefined>;

Defined in: async-throttler.ts:462

Processes the current pending execution immediately

Returns

Promise<ReturnType<TFn> | undefined>

getAbortSignal()

getAbortSignal(maybeExecuteCount?): AbortSignal | null;

Defined in: async-throttler.ts:523

Returns the AbortSignal for a specific execution. If no maybeExecuteCount is provided, returns the signal for the most recent execution. Returns null if no execution is found or not currently executing.

Parameters

maybeExecuteCount?

number

Optional specific execution to get signal for

Returns

AbortSignal | null

Example

const throttler = new AsyncThrottler(
  async (data: string) => {
    const signal = throttler.getAbortSignal()
    if (signal) {
      const response = await fetch('/api/save', {
        method: 'POST',
        body: data,
        signal
      })
      return response.json()
    }
  },
  { wait: 1000 }
)

maybeExecute()

maybeExecute(...args): Promise<ReturnType<TFn> | undefined>;

Defined in: async-throttler.ts:338

Attempts to execute the throttled function. The execution behavior depends on the throttler options:

If enough time has passed since the last execution (>= wait period):
- With leading=true: Executes immediately
- With leading=false: Waits for the next trailing execution
If within the wait period:
- With trailing=true: Schedules execution for end of wait period
- With trailing=false: Drops the execution

Parameters

args

...Parameters<TFn>

Returns

Promise<ReturnType<TFn> | undefined>

Example

const throttled = new AsyncThrottler(fn, { wait: 1000 });

// First call executes immediately
await throttled.maybeExecute('a', 'b');

// Call during wait period - gets throttled
await throttled.maybeExecute('c', 'd');