throttle-async-rxjs-pipe

A pipe functions for rxjs 7+ which accepts a 'wait' observable, emits 1 elements of the source stream and waits for an event on the 'wait' observable.

What does throttleAsync do (in order)?

1. Get a waitUntil$ observable as parameter
2. Emit one value (may be configurable in the future)
3. Wait until waitUntil$ observable emits a value.
4. If waitUntil$ emits a value, emit another value from the source observable.

Why is this useful?

I personally need it for splitting up resize events from the browser into a resize-start and a resize-end observable.

First, we need an observable of window resize events:

const windowResize$ = fromEvent(window, 'resize');

We can produce a resize-end observable by

const windowResizeEnd$ = windowResize$.pipe(debounceTime(500));

But how would you build the windowResizeStart$ observable? This is, where the throttleAsync pipe comes in.
We need windowResize$ to emit exactly one event and then pause emission
until windowResizeEnd$ emits a value.

    const windowResizeStart$ = windowResize$.pipe(
        throttleAsync(windowResizeEnd$)
    );

Future Features (eventually)

• Emit n source events between waitUntil$ observable emissions instead of only one.
  The parameter n should be configureable when instantiating throttleAsync.
• Make the parameter n dynamic by using the value of the waitUntil$ observable as a number of how many events to emit next.
• Add https://github.com/xripcsu/rxjs-watcher to help visualize the function of these operators

Tooling

• tsup bundler docs: https://paka.dev/npm/tsup@8.0.2/api
• tsup website: https://tsup.egoist.dev/

Changelog

[1.2.1] - 2024-04-16

• Fix rxjs version in README.md

[1.2.0] - 2024-04-16

Breaking Change: Lib now requires rxjs 7.0.0 or higher!

• Switched to tsup for building the library, which unlocks lot more formats for consuming the library:
  • dist/index.js (ES2020, CJS)
  • dist/index.mjs (ES2020, ESM)
  • dist/index.d.ts (Typescript Typings)
  • src/* (Typescript Source)

[1.1.0] - 2020-04-13

• Updated Dependencies to fix dependency security issues
• Improved npm packaging for easier usage

[1.0.0] - 2018-11-12

Initial Release

Features

• throttleAsync pipe which emits one event and then waits for waitUntil$ observable emissions