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Runs promises yielded by generators in parallel

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JSR Score
3 weeks ago
deno add @reda/parallelize-generator-promises
import * as mod from "@reda/parallelize-generator-promises";
npx jsr add @reda/parallelize-generator-promises
import * as mod from "@reda/parallelize-generator-promises";
yarn dlx jsr add @reda/parallelize-generator-promises
import * as mod from "@reda/parallelize-generator-promises";
pnpm dlx jsr add @reda/parallelize-generator-promises
import * as mod from "@reda/parallelize-generator-promises";
bunx jsr add @reda/parallelize-generator-promises
import * as mod from "@reda/parallelize-generator-promises";


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A simple utility to run promises yielded by a generator in parallel. This is incredibly useful when you need to run a bunch of tasks as fast as possible without waiting for one another.


parallelize-generator-promises is available on both npm and JSR.

To use from npm, install the parallelize-generator-promises package and then import into a module:

import { parallelizeGeneratorPromises } from "parallelize-generator-promises";

To use from JSR, install the @reda/parallelize-generator-promises package and then import into a module:

import { parallelizeGeneratorPromises } from "@reda/parallelize-generator-promises";

Polyfilling Promise.withResolvers

If you are using Node.js v20 or below, you will require a polyfill for Promise.withResolvers.

A polyfill for this is available in a separate export as part of this package. To use the provided polyfill, import it at the entrypoint of your application.


import "parallelize-generator-promises/promise-with-resolvers-polyfill";


import "@reda/parallelize-generator-promises/promise-with-resolvers-polyfill";


import { parallelizeGeneratorPromises } from "parallelize-generator-promises";

async function* getAllProductDetails() {
  for (let page = 1; page <= 100; page++) {
    const products = await fetch(`/products?page=${page}`).then((res) =>
    yield =>
      fetch(`/product/${}/details`).then((res) => res.json())

for await (
  const productDetails of parallelizeGeneratorPromises(
) {

The above example will fetch all product details for one page of products at a time as fast as possible, yielding the product details in the fastest order possible to keep the iterator fed.

If a concurrency limit is required, this utility pairs very well with a semaphore library such as async-sema.


Name Description
maxBufferedPromises Limits the maximum number of promises that can be buffered at any given time. Useful to manage memory usage in the case where you are generating a lot of promises that aren't being consumed at a fast enough rate. NOTE: this value must be greater than or equal to 1. By default this is undefined which means there is no limit set.
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