p-throttle

Throttle promise-returning & async functions

It also works with normal functions.

It rate-limits function calls without discarding them, making it ideal for external API interactions where avoiding call loss is crucial.

npm install p-throttle

Here, the throttled function is only called twice a second:

import pThrottle from 'p-throttle';

const now = Date.now();

const throttle = pThrottle({
	limit: 2,
	interval: 1000
});

const throttled = throttle(async index => {
	const secDiff = ((Date.now() - now) / 1000).toFixed();
	return `${index}: ${secDiff}s`;
});

for (let index = 1; index <= 6; index++) {
	(async () => {
		console.log(await throttled(index));
	})();
}
//=> 1: 0s
//=> 2: 0s
//=> 3: 1s
//=> 4: 1s
//=> 5: 2s
//=> 6: 2s

Returns a throttle function.

Type: object

Both the limit and interval options must be specified.

Type: number

The maximum number of calls within an interval.

Type: number

The timespan for limit in milliseconds.

Type: boolean
Default: false

Use a strict, more resource intensive, throttling algorithm. The default algorithm uses a windowed approach that will work correctly in most cases, limiting the total number of calls at the specified limit per interval window. The strict algorithm throttles each call individually, ensuring the limit is not exceeded for any interval.

Type: AbortSignal

Abort pending executions. When aborted, all unresolved promises are rejected with signal.reason.

import pThrottle from 'p-throttle';

const controller = new AbortController();

const throttle = pThrottle({
	limit: 2,
	interval: 1000,
	signal: controller.signal
});

const throttled = throttle(() => {
	console.log('Executing...');
});

await throttled();
await throttled();
controller.abort('aborted')
await throttled();
//=> Executing...
//=> Executing...
//=> Promise rejected with reason `aborted`

Type: Function

Get notified when function calls are delayed due to exceeding the limit of allowed calls within the given interval. The delayed call arguments are passed to the onDelay callback.

Can be useful for monitoring the throttling efficiency.

In the following example, the third call gets delayed and triggers the onDelay callback:

import pThrottle from 'p-throttle';

const throttle = pThrottle({
	limit: 2,
	interval: 1000,
	onDelay: (a, b) => {
		console.log(`Reached interval limit, call is delayed for ${a} ${b}`);
	},
});

const throttled = throttle((a, b) => {
	console.log(`Executing with ${a} ${b}...`);
});

await throttled(1, 2);
await throttled(3, 4);
await throttled(5, 6);
//=> Executing with 1 2...
//=> Executing with 3 4...
//=> Reached interval limit, call is delayed for 5 6
//=> Executing with 5 6...

Returns a throttled version of function_.

Type: Function

A promise-returning/async function or a normal function.

Type: boolean
Default: true

Whether future function calls should be throttled and count towards throttling thresholds.

Type: number

The number of queued items waiting to be executed.

• p-debounce - Debounce promise-returning & async functions
• p-limit - Run multiple promise-returning & async functions with limited concurrency
• p-memoize - Memoize promise-returning & async functions
• More…