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subscribable-things

A collection of reactive wrappers for various browser APIs.


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.

Usage

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

``shell
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 ...

`js
import { mediaQueryMatch } from 'subscribable-things';

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

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

unsubscribe();
`

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

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

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

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

subscription.unsubscribe();
`

... or Callbags ...

`js
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 ...

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

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

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

unsubscribe();
`

... or Bacon.js ...

`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));

unsubscribe();
`

... or Kefir.js.

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

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

const subscription = stream.observe({
value(isMatching) {
console.log(isMatching);
}
});

subscription.unsubscribe();
`

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

`js
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$)) {
console.log(isMatching);
}
`

Also it's possible to output values directly to HTML via hyperf.

`js
import h from 'hyperf';
import { mediaQueryMatch } from 'subscribable-things';

const element = h

document.body.appendChild(element);
`

$3

`ts
function animationFrame(): SubscribableThing;
`

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

$3

`ts
function attribute(htmlElement: HTMLElement, name: string): TSubscribableThing;
`

This function uses mutations() on the inside to emit the latest value of the attribute with the given name.

$3

`ts
function geolocation(options?: PositionOptions): SubscribableThing;
`

This is a wrapper for the Geolocation API. It uses watchPosition() to gather the most recent GeolocationPosition whenever it changes.

$3

`ts
function intersections(
htmlElement: HTMLElement,
options?: IntersectionObserverInit
): SubscribableThing;
`

This function is a wrapper for the IntersectionObserver.

$3

`ts
function mediaDevices(): SubscribableThing;
`

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.

$3

`ts
function mediaQueryMatch(mediaQueryString: string): SubscribableThing;
`

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

$3

`ts
function midiInputs(midiAccess: IMidiAccess): SubscribableThing;
`

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

$3

`ts
function midiOutputs(midiAccess: IMidiAccess): SubscribableThing;
`

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

$3

`ts
function metrics(options: PerformanceObserverInit): SubscribableThing;
`

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

$3

`ts
function mutations(
htmlElement: HTMLElement,
options: MutationObserverInit
): SubscribableThing;
`

This function is a wrapper for the MutationObserver.

$3

`ts
function on(
target: EventTarget,
type: string,
options?: boolean | AddEventListenerOptions
): SubscribableThing;
`

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

$3

`ts
function online(): SubscribableThing;
`

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

$3

`ts
function permissionState(
permissionDescriptor: PermissionDescriptor
): SubscribableThing;
`

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.

$3

`ts
function reports(options?: IReportingObserverOptions): SubscribableThing;
`

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

$3

`ts
function resizes(
htmlElement: HTMLElement,
options?: IResizesObserverOptions
): SubscribableThing;
`

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

$3

`ts
function unhandledRejection(coolingOffPeriod: number): SubscribableThing;
`

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.

$3

`ts
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.

$3

`ts
function wakeLock(type: TWakeLockType): SubscribableThing;
``

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.

Alternatives

There are two similar packages available which are based directly on RxJS. They are rx-use and rxjs-web.