src / mixin / operators.js

Copyright (c) 2018 Florian Klampfer

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see

import { never } from "rxjs/_esm5/observable/never";

import { filter } from "rxjs/_esm5/operators/filter";
import { map } from "rxjs/_esm5/operators/map";
import { switchMap } from "rxjs/_esm5/operators/switchMap";
import { withLatestFrom } from "rxjs/_esm5/operators/withLatestFrom";

Observable extensions

Subscribe when

This operator is like filterWhen, but it will unsubscribe from the source observable when the input observable emits false, and re-subscribe when it emits true.

export const subscribeWhen = p$ => source => {
  if (process.env.DEBUG && !p$) throw Error();
  return p$.pipe(switchMap(p => (p ? source : never())));

Filter when

This operator is like filter, but it takes an observable of booleans as input, instead of a predicate function.

export const filterWhen = (p$, ...others) => source => {
  if (process.env.DEBUG && !p$) throw Error();
  else if (others.length === 0) {
    return source.pipe(withLatestFrom(p$), filter(([, p]) => p), map(([x]) => x));

When providing more than one observable, the result observable will only emit values when every input observable has emitted a truthy value.

  } else {
    return source.pipe(
      withLatestFrom(p$, ...others),
      filter(([,]) => ps.every(p => p)),
      map(([x]) => x)

© 2018 Florian Klampfer

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