p-throttle

What is p-throttle?

The p-throttle npm package is used to throttle the execution of asynchronous functions. It allows you to limit the number of times a function can be called over a specified period, which is useful for rate-limiting API requests or controlling the flow of operations in a system.

What are p-throttle's main functionalities?

Basic Throttling

This feature allows you to throttle the execution of a function. In this example, the function can only be called twice per second.

const pThrottle = require('p-throttle');

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

const throttled = throttle(async (index) => {
  console.log(index);
});

(async () => {
  for (let i = 0; i < 10; i++) {
    throttled(i);
  }
})();

Throttling with Promises

This feature demonstrates throttling with asynchronous functions that return promises. The function is throttled to execute once every two seconds.

const pThrottle = require('p-throttle');

const throttle = pThrottle({ limit: 1, interval: 2000 });

const throttled = throttle(async (index) => {
  return new Promise((resolve) => {
    setTimeout(() => {
      console.log(index);
      resolve();
    }, 1000);
  });
});

(async () => {
  for (let i = 0; i < 5; i++) {
    await throttled(i);
  }
})();

Other packages similar to p-throttle

bottleneck

Bottleneck is a powerful rate limiter that can be used to control the rate of asynchronous operations. It offers more advanced features like clustering and priority queues, making it more suitable for complex scenarios compared to p-throttle.

limiter

Limiter is another rate-limiting library that provides a simple way to limit the number of operations over a given time period. It is similar to p-throttle but offers a more straightforward API for basic use cases.

rate-limiter-flexible

Rate-limiter-flexible is a highly flexible rate-limiting library that supports various backends like Redis and MongoDB. It provides more configuration options and is suitable for distributed systems, offering more flexibility than p-throttle.

README

p-throttle

Throttle promise-returning & async functions

It also works with normal functions.

Useful for rate limiting calls to an external API, for example.

Install

$ npm install p-throttle

Usage

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

const pThrottle = require('p-throttle');

const now = Date.now();

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

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

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

API

pThrottle(options)

Returns a throttle function.

Returns a throttled version of fn.

options

Type: object

Both the limit and interval options must be specified.

limit

Type: number

Maximum number of calls within an interval.

interval

Type: number

Timespan for limit in milliseconds.

strict

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.

throttle(function_)

function_

Type: Function

Promise-returning/async function or a normal function.

throttledFn.abort()

Abort pending executions. All unresolved promises are rejected with a pThrottle.AbortError error.

throttledFn.isEnabled

Type: boolean
Default: true

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

Related

• 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…