https://github.com/layzeedk/rxjs-subscription-count

subscriptionCount operator for RxJS - Count subscriptions to observables. Useful for testing.
https://github.com/layzeedk/rxjs-subscription-count

rxjs rxjs-subscriptions rxjs6

Last synced: about 2 months ago
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subscriptionCount operator for RxJS - Count subscriptions to observables. Useful for testing.

• Host: GitHub
• URL: https://github.com/layzeedk/rxjs-subscription-count
• Owner: LayZeeDK
• Created: 2018-08-03T23:58:06.000Z (over 6 years ago)
• Default Branch: develop
• Last Pushed: 2022-03-02T23:01:07.000Z (almost 3 years ago)
• Last Synced: 2024-10-30T11:20:16.882Z (2 months ago)
• Topics: rxjs, rxjs-subscriptions, rxjs6
• Language: TypeScript
• Size: 186 KB
• Stars: 6
• Watchers: 2
• Forks: 2
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • Funding: .github/FUNDING.yml

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README

        
# `subscriptionCount` operator for RxJS

## rxjs-subscription-count

Count subscriptions to observables. Useful for testing `Observable` flattening strategies.

## Installation

Install using NPM CLI

```

npm install --save rxjs-subscription-count

```

or using Yarn CLI

```

yarn add rxjs-subscription-count

```

## Use cases

Test that the subscriptions are switched (`switchMap` or `switchAll`) correctly

to prevent memory leaks and race conditions.

## Usage

```typescript

import { BehaviorSubject, empty } from 'rxjs';

import { subscriptionCount } from 'rxjs-subscription-count';

const counter: BehaviorSubject = new BehaviorSubject(0);

const source: Observable = empty().pipe(

  subscriptionCount(counter),

);

```

## `switchMap` test case

```typescript

import {

  BehaviorSubject,

  interval,

  Observable,

  range,

  Subscription,

} from 'rxjs';

import { switchMap } from 'rxjs/operators';

import { subscriptionCount } from './subscription-count';

describe('switchMap', () => {

  it('keeps a single subscription', () => {

    const threeValues: Observable = range(1, 3);

    const subscriptionCounter: BehaviorSubject = new BehaviorSubject(0);

    const infiniteValues: Observable = interval(0).pipe(

      subscriptionCount(subscriptionCounter),

    );

    const subscription: Subscription = threeValues.pipe(

      switchMap(() => infiniteValues),

    ).subscribe();

    expect(subscriptionCounter.value).toBe(1);

    subscription.unsubscribe();

  });

});

```

## `mergeMap` test case

```typescript

import {

  BehaviorSubject,

  interval,

  Observable,

  range,

  Subscription,

} from 'rxjs';

import { mergeMap } from 'rxjs/operators';

import { subscriptionCount } from './subscription-count';

describe('mergeMap', () => {

  it('results in a subscription per emitted value', () => {

    const threeValues: Observable = range(1, 3);

    const subscriptionCounter: BehaviorSubject = new BehaviorSubject(0);

    const infiniteValues: Observable = interval(0).pipe(

      subscriptionCount(subscriptionCounter),

    );

    const subscription: Subscription = threeValues.pipe(

      mergeMap(() => infiniteValues),

    ).subscribe();

    expect(subscriptionCounter.value).toBe(3);

    subscription.unsubscribe();

  });

});

```