@jsonxr/promises

PromisePool

yarn add @jsonxr/promises

A pool of promises that will limit the number of executions that will concurrently execute. If you are making API calls using the standard built-in promises, all the promises are executed simultaneously which can cause problems with rate limiting. This will limit the number of concurrent executions.

all(array, options)

Performs the same function as Promise.all but throttles the creation of promises and limits the number of concurrent promises.

Parameters

• array - An array of functions that create promises
• options -
  • limit - Maximum number of promises (default 6, chrome concurrent requests)
  • throttle - number of ms to wait before creating the promise (default 0)

Example

import { all } from '@jsonxr/promises';

const fn = async (i) => i;

const promises = []
promises.push(() => fn(1));
promises.push(() => fn(2));
promises.push(() => fn(3));
promises.push(() => fn(4));
all(promises, { limit: 2, throttle: 100 })
  .then(results => console.log(results))

output

[1,2,3,4]

allSettled

import { allSettled } from '@jsonxr/promises';

const fn = async (i) => {
  if (i % 2 !== 0) throw new Error("That's odd");
  return i;
};

const promises = []
promises.push(() => fn(1));
promises.push(() => fn(2));
promises.push(() => fn(3));
promises.push(() => fn(4));
allSettled(promises, { limit: 2, throttle: 100 })
  .then(results => console.log(results))

output

[
  { status: 'rejected', reason: Error: That's odd },
  { status: 'fulfilled', value: 2 },
  { status: 'rejected', reason: Error: That's odd },
  { status: 'fulfilled', value: 4 }
]

Do not do this

Promises are scheduled for execution the moment they are created. promises therefore expects a promise creator function, not a promise.

const fn = async (i) => i; // Promise function

const promises = [];

// Do this
promises.push(() => fn(1));

// ERROR. Don't do this!!!
promises.push(fn(1));