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subscribable-thingsTypeScript icon, indicating that this package has built-in type declarations

1.11.3 • Public • Published



A collection of reactive wrappers for various browser APIs.

tests dependencies version

This package provides factory functions which can be used to turn browser APIs into subscribable things. A subscribable thing can either be consumed directly with callback functions or by utilzing one of the popular libraries for reactive programming.


The subscribable-things package is published on npm and can be installed as usual.

npm install subscribable-things

It exports individual functions for each wrapped browser API which are described in greater detail below. They can either be used directly by providing a callback function ...

import { mediaQueryMatch } from 'subscribable-things';

const subscribe = mediaQueryMatch('(max-width:600px)');

const unsubscribe = subscribe((isMatching) => console.log(isMatching));


... or by utilizing a library for reactive programming like RxJS ...

import { from } from 'rxjs';
import { mediaQueryMatch } from 'subscribable-things';

const mediaQueryMatch$ = from(mediaQueryMatch('(max-width:600px)'));

const subscription = mediaQueryMatch$.subscribe((isMatching) => console.log(isMatching));


... or Callbags ...

import fromObs from 'callbag-from-obs';
import observe from 'callbag-observe';
import { mediaQueryMatch } from 'subscribable-things';

const source = fromObs(mediaQueryMatch('(max-width:600px)'));

observe((isMatching) => console.log(isMatching))(source);

... or XStream ...

import { mediaQueryMatch } from 'subscribable-things';
import { fromObservable } from 'xstream';

const stream = fromObservable(mediaQueryMatch('(max-width:600px)'));

const unsubscribe = stream.subscribe((isMatching) => console.log(isMatching));


... or Bacon.js ...

import { fromESObservable } from 'baconjs';
import { mediaQueryMatch } from 'subscribable-things';

const eventStream = fromESObservable(mediaQueryMatch('(max-width:600px)'));

const unsubscribe = eventStream.onValue((isMatching) => console.log(isMatching));


... or Kefir.js.

import { fromESObservable } from 'kefir';
import { mediaQueryMatch } from 'subscribable-things';

const stream = fromESObservable(mediaQueryMatch('(max-width:600px)'));

const subscription = stream.observe({
    value(isMatching) {


It is even possible to consume subscribable-things as an async iterable by taking the little detour over RxJS and rxjs-for-await.

import { eachValueFrom } from 'rxjs-for-await';
import { from } from 'rxjs';
import { mediaQueryMatch } from 'subscribable-things';

const source$ = from(mediaQueryMatch('(max-width:600px)'));

for await (const isMatching of eachValueFrom(source$)) {

animationFrame(): SubscribableThing<number>

This function wraps the requestAnimationFrame() method. It emits the current timestamp of each animation frame.

intersections(htmlElement: HTMLElement, options?: IntersectionObserverInit): SubscribableThing<IntersectionObserverEntry[]>

This function is a wrapper for the IntersectionObserver.

mediaDevices(): SubscribableThing<MediaDeviceInfo[]>

This function is a wrapper for the enumerateDevices() method of the Media Capture and Streams specification. It will also listen for the devicechange event to emit a fresh list of devices whenever they change.

mediaQueryMatch(mediaQueryString: string): SubscribableThing<boolean>

This function is a wrapper for the matchMedia() method. It will emit a new value whenever the result of matchMedia() changes.

midiInputs(midiAccess: IMidiAccess): SubscribableThing<IMidiInput[]>

This function returns the currently available MIDI input devices. It accepts a MIDIAccess object of the Web MIDI API.

midiOutputs(midiAccess: IMidiAccess): SubscribableThing<IMidiOutput[]>

This function returns the currently available MIDI output devices. It accepts a MIDIAccess object of the Web MIDI API.

metrics(options: PerformanceObserverInit): SubscribableThing<PerformanceEntry[]>

This function is a wrapper for the PerformanceObserver as defined by the Performance Timeline Level 2 specification.

mutations(htmlElement: HTMLElement, options: MutationObserverInit): SubscribableThing<MutationRecord[]>

This function is a wrapper for the MutationObserver.

on(target: EventTarget, type: string, options?: boolean | AddEventListenerOptions): SubscribableThing<Event>

This function can be used to subscribe to events of a certain type dispatched from an EventTarget.

online(): SubscribableThing<boolean>

This function wraps the onLine property of the Navigator and listens for the corresponding 'online' and 'offline' events on the Window to emit updates.

permissionState(permissionDescriptor: PermissionDescriptor): SubscribableThing<PermissionState>

This function is a wrapper for the query() method of the Permissions API. It will monitor the permission status to emit a new state whenever it gets updated.

reports(options?: IReportingObserverOptions): SubscribableThing<IReport[]>

This function is a wrapper for the ReportingObserver of the Reporting API.

resizes(htmlElement: HTMLElement, options?: IResizesObserverOptions): SubscribableThing<IResizeObserverEntry[]>

This function is a wrapper for the ResizeObserver of the Resize Observer specification.

unhandledRejection(coolingOffPeriod: number): SubscribableThing<any>

This function emits unhandled rejections. It will listen for the unhandledrejection event to register possibly unhandled rejections. It will then wait for the cooling-off period to elapse before it emits the reason (aka the error) that caused the unhandled rejection. It is possible that a previously unhandled rejection gets handled later on in which case a rejectionhandled event will be fired. If that happens during the cooling-off period nothing will be emitted by this function.

videoFrame(videoElement: HTMLVideoElement): SubscribableThing<{ now: number } & IVideoFrameMetadata>

This function wraps the requestVideoFrameCallback() method of the given HTMLVideoElement. It emits the current timestamp combined with the VideoFrameMetadata object.

wakeLock(type: TWakeLockType): SubscribableThing<boolen>

This function simplifies the usage of the Screen Wake Lock API. It emits true when a wake lock could be acquired and emits false once the wake lock gets released by the browser. As long as the subscription is alive it will continuosly try to get a new wake lock if the current one gets released.


npm i subscribable-things

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