use-rxjs-effect

Size: 6.25 kB with all dependencies, minified and gzipped as ESM module

When creating effects in React with useEffect and Promises, setTimeout or setInterval, you can run into various problems. When effects still execute after the component unmounts, it can lead to:

• Wasted bandwidth uploading or downloading what the user may not be interested in anymore.
• Errors thrown when effects update DOM nodes that that don't exist after unmount.

And when useEffect is triggered on a change of dependencies:

• You are limited in concurrency options (you can not easily queue or throttle effects)
• Cancelation of a previous effect only runs after a render cycle (leading to race conditions ala the Kent C Dodds setInterval problem here)

Adding AbortController-based code to Promises is only a band-aid, and bloats your code. But Observables (from RxJS) are fundamentally cancelable, are concise to read, and have a full range of concurrency options. use-rxjs-effect exists to bring the benefits of RxJS Observables to React's useEffect.

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API

These methods, sharing the same signature, allow you to transparently apply component-based cancelation, and RxJS concurrency modes, to effects:

• useASAPEffect - Runs effects in parallel as order-independent, unconstrained effects. Use Case: Like Buttons. RxJS operator: mergeMap
• useQueuedEffect - Runs effects serially, with a maximum concurrency of 1. Use Case: Analytics Events, ensure arrival order is consistent with sending order. RxJS operator: concatMap
• useDebouncedEffect - Runs an effect with a maximum concurrency of 1, canceling any previously running effect. Wrap the returned Observable with after(N, effectObservable) to apply a debounce delay. Use Case: A typeahead/autocomplete search box. RxJS operator: switchMap
• useThrottledEffect - Runs an effect with a maximum concurrency of 1.Refrainins from starting a new effect if one is already running. Wrap the returned Observable with concat(effectObservable, after(N)) to add to the throttling delay. Use Case: Prevent double-submission of a form. RxJS operator: exhaustMap
• useCancelableEffect - Alias for useASAPEffect. Use Case: Ensure component initialization is canceled if component is unmounted.

The usage pattern for these hooks is:

const [triggerFn] = useCancelableEffect((value: string) => {
  return new Observable(() => {
    // do the work

    return () => // cancel the work
  });
});

The return tuple contains a stable function that can be used to trigger the effect in event handlers or useEffects, assured that cancelation and the correct concurrency will be applied.

<input onChange={(e) => triggerFn(e.target.value)}>

Note that your Observable-returning function can be imported from another library (e.g. RxJS, or a custom one), and need not have any dependency on React. You can concat or pipe(tap) onto the Observable to apply React-specific behaviors like calling state-setters. See the example/ folder for more.

Utilities:

• after(msec, value | fn | Observable) - Creates an Observable of a value, the return value of a function, or another Observable, delayed by the number of milliseconds given. Can be await-ed.
• concat - A re-export of RxJS' concat, for creating chains of Observables with composed cancelation and values.

Examples

See executable code in the example/ directory of this project.

cd example; yarn && yarn start

Timing Diagrams

The usefulness of these fundamental modes of combining async effects can be illustrated (thanks to Ember Concurrency for the originals)

ASAP

Queued

Debounced

Throttled

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Inspiration and References

• Ember Concurrency
• ReactiveX
• RxJS