Strict Throttle

Strictly delays (rate limits) the execution of function calls, ensuring the function calls are executed no faster than the supplied limit times within a given interval. The strict throttle operates with a rolling window, such that no more than limit calls are ever executed within any period of time equal to the interval.

Install

$ npm install strict-throttle

Example

const throttle = require('strict-throttle')({limit: 2, interval: 1000});
const delay = require('delay');

async function example () {
    const start = Date.now();
    
    function elapsedTime () {
        return Date.now() - start;
    }

    throttle(elapsedTime).then(console.log); // 0
    await delay(950);
    throttle(elapsedTime).then(console.log); // 950
    throttle(elapsedTime).then(console.log); // 1000
    throttle(elapsedTime).then(console.log); // 1950
    throttle(elapsedTime).then(console.log); // 2000
    
    throttle.waitingCount(); // 3
    
    //throttle.abort(); to reject waiting calls
}

example();

Similar libraries often use a windowed algorithm, allowing limit executions per interval. This is sufficient for most use cases, but may result in the overuse of the limited resource when bursts are encountered.

API

StrictThrottle(options)

Returns a throttle function that delays the execution of function calls according the constraints in the options. When executed, the throttle returns a Promise that resolves to return value of the supplied function.

options

Type: object

Both the limit and interval options must be specified.

limit

Type: number

Constraint: Must be a positive integer

Maximum number of calls within an interval.

interval

Type: number

Constraint: Must be a positive integer

Timespan for limit in milliseconds.

throttle.waitingCount()

Return the number of calls waiting to be executed.

throttle.abort()

Abort pending executions. All calls waiting to be executed are rejected. Note: any ongoing calls that have been executed are not affected.

Credits

Original author: Aaron Schinkowitch

Inspired by p-throttle.