npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

rxjs-for-await

v1.0.0

Published

Add async-await for-await loop support to RxJS Observables

Downloads

1,143,554

Readme

CI npm version License: MIT

rxjs-for-await

A library for making RxJS support async-await for-await loops via AsyncIterables

Four Strategies

This library exposes 4 different ways to consume an RxJS observable with an async/await for await..of loop using AsyncIterable. Each of these strategies has pros and cons, so be aware of those as you choose the one that suits your needs.

eachValueFrom (lossless)

async function example() {
  const source$ = interval(100);

  for await (const value of eachValueFrom(source$)) {
    console.log(value);
  }
}

This strategy will yield every single value the observable source emits, one at a time, until the observable completes or errors.

Pros

  • All values are yielded
  • You get each value one at a time

Cons

  • Creates more memory pressure if the body of the for await loop takes longer to come back around than the time between emissions from the observable source. If the observable emits faster than your loop can consume them, this may result in a memory leak.

bufferedValuesFrom (lossless)

async function example() {
  const source$ = interval(10);

  for await (const buffer of bufferedValuesFrom(source$)) {
    console.log(buffer);
    await wait(1000);
  }
}

Keep an internal buffer of values emitted by the observable source, and yield the entire buffer to the for await loop. Continue this until the observable source completes or errors.

Pros

  • All values are yielded
  • Lower memory pressure than eachValueFrom
  • Provides snapshots of what has happened since the last loop

Cons

  • May still cause out of memory errors if the body of the for await loop is extremely slow.
  • Perhaps less intuitive than eachValueFrom.

latestValueFrom (lossy)

async function example() {
  const source$ = interval(100);

  for await (const value of latestValueFrom(source$)) {
    console.log(value);
  }
}

This strategy will immediately yield the most recently arrived value, or the very next one, if the for await loop is waiting and one has not arrived yet. Will continue to do so until the source observable completes or errors.

Pros

  • No chance of memory leaks
  • Quick entry to the loop if a value is already available

Cons

  • Will lose values if more than one value arrives while the loop body is being processed.

nextValueFrom (lossy)

async function example() {
  const source$ = interval(100);

  for await (const value of nextValueFrom(source$)) {
    console.log(value);
  }
}

Will wait for the very next value to arrive, then yield it. Will continue to do so until the source observable completes or errors.

Pros

  • No chance of memory leaks

Cons

  • Loop must wait for the next value to arrive, perhaps slowing down the process
  • Will lose values if values arrive while the loop is being processed.