https://github.com/justinfagnani/async-broadcaster

Observable alternative using async iterators
https://github.com/justinfagnani/async-broadcaster

Last synced: about 2 months ago
JSON representation

Observable alternative using async iterators

• Host: GitHub
• URL: https://github.com/justinfagnani/async-broadcaster
• Owner: justinfagnani
• License: mit
• Created: 2021-06-24T00:42:32.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2021-06-24T04:58:42.000Z (over 3 years ago)
• Last Synced: 2024-10-26T15:06:49.757Z (2 months ago)
• Language: TypeScript
• Size: 50.8 KB
• Stars: 17
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

README

        
# async-broadcaster

Observable alternative using async iterators

## Install

```sh

npm i async-broadcaster

```

## Why

It's a common requirement to let users subscribe to new values that are produced asynchronously. Often we reach for an observable library (RxJS, zen-observable, Wonka, etc.) to manage subscriptions and allow broadcasting of new values, but full observable implementations may be overkill for simple subscriptions. Observable also bring along a new API, when JavaScript already has an standard API for _consuming_ asynchronous values: [async iterables](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of).

What's needed to enable consumers to use async iterables is a way for producers to make async iterables that can be listened to by multiple listeners and correctly handle buffering, unsubscription, etc.

This is what AsyncBroadcaster does.

AsyncBroadcaster takes a single async iterable and adapts it to allow multiple listeners.

## Features

- Supports multiple listeners

- Buffers values for slow listeners

- Efficiently clears the buffer of values seen by all listeners

- Supports AbortSignal for cancelling iteration

- Automatically cleans up when listeners break or return from for/await...of loops

## Usage

```ts

import {AsyncBroadcaster} from 'async-broadcaster';

async function* makeOneHundred() {

  for (let i = 0; i < 100; i++) {

    yield i;

  }

}

const broadcaster = new AsyncBroadcaster(makeOneHundred());

// listen to broadcast values

logValues(broadcaster.iterable);

// We can listen more than once

logValues(broadcaster.iterable);

async function logValues(iterable) {

  // listening is done with anything that can consume async iterables, like

  // a for/await-of loop:

  for await (const o of iterable) {

    console.log(o);

  }

}

```

### Pairs well with IxJS

Async iterables don't have the functional methods that Array does like `map()`, `reduce()`, or `filter()`, nor the common reactive operators like `count()`, `zip()`, etc.

These can be imported from a library that works with any async iterable, such as [IxJS](https://github.com/ReactiveX/IxJS).

```ts

import { filter, map } from 'ix/asynciterable/operators';

const results = from(broadcaster.iterable).pipe(

  filter(async x => x % 2 === 0),

  map(async x => x * x)

);

for await (let item of results) {

  console.log(`Next: ${item}`);

}

```