@zeit-dev/rxjs-util

This is a small and incoherent collection of RxJS operators we commonly commonly use across our projects.

Installation

npm add @zeit-dev/rxjs-util

or

yarn add @zeit-dev/rxjs-util

Operators

[[allTrue]]

Combine several boolean observables, and return true if all latest values are true, false otherwise.

  allTrue(of(false), of(true)).subscribe((x) => console.log(x))
  // => false

[[filterTruthy]]

This is basically just filter(x => !!x) with the added benefit of collapsing an input type of T | undefined to just T

  of(true, false, '', 0, null, undefined, true, 'a', 1).pipe(filterTruthy()).subscribe((x) => console.log(x));
  // => true, true, 'a', 1

[[flip]]

Just a shortcut for map(x => !x)

  of(true).pipe(flip()).subscribe((x) => console.log(x));
  // => false

[[log]]

This is a debug tool, that taps into the observable stream, and uses console.log to output each event, and console.error for errors. To identify the log output, you can specify a log category/tag:

  interval(1000).pipe(log('Here')).subscribe()
  // => Here 1, Here 2, Here 3

[[mapVoid]]

Casts observable to Observable<void>.

[[replayWhile]]

Replays the last value every n miliseconds until the next value arrives. Stops replaying when predicate evaluates to false.

[[returnToZone]]

Helper to return to the Angular zone (NgZone), when an event arrives. Useful if you have external async sources.

  // inject ngZone: NgZone
  from(someExternalPromise).pipe(returnToZone(ngZone))

[[switchCombine]]

SwitchMap to an inner observable and carry the current value into the output. Same as

  switchMap((x) => innerObservable.pipe(map((y) => [x, y])))

[[takeWhileInclusive]]

Same as takeWhile but emits the last event as well.