https://github.com/pietile/pietile-promise-observer

Simple Promise observer
https://github.com/pietile/pietile-promise-observer

observer promise

Last synced: about 20 hours ago
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Simple Promise observer

• Host: GitHub
• URL: https://github.com/pietile/pietile-promise-observer
• Owner: pietile
• Created: 2019-02-03T17:10:08.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2021-02-15T10:37:11.000Z (almost 4 years ago)
• Last Synced: 2024-04-23T10:45:24.703Z (9 months ago)
• Topics: observer, promise
• Language: TypeScript
• Size: 16.6 KB
• Stars: 1
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Pietile Promise Observer

[![npm version](https://badgen.net/npm/v/pietile-promise-observer?color=56C838)](https://www.npmjs.com/package/pietile-promise-observer)

[![install size](https://badgen.net/packagephobia/install/pietile-promise-observer)](https://packagephobia.now.sh/result?p=pietile-promise-observer)

As Promise can't be canceled we can just unsubscribe from its result when don't need it.

## Installation

Using yarn

```sh

yarn add pietile-promise-observer

```

or using npm

```sh

npm install -S pietile-promise-observer

```

## Usage example

```tsx

import { PromiseObserver, PromiseResult } from "pietile-promise-observer";

function asyncAction(): Promise {

  return new Promise((resolve) => {

    setTimeout(() => {

      resolve(Math.random());

    }, 1000);

  });

}

function resultHandler(result: PromiseResult): void {

  if (result.error) {

    // Smth wrong happened

    console.log("Error :(", result.error.message);

    return;

  }

  console.log(result.value + 1);

}

const promiseObserver = new PromiseObserver();

promiseObserver.subscribe(asyncAction(), resultHandler);

// Somehwere later ...

promiseObserver.subscribe(asyncAction(), resultHandler);

// or

promiseObserver.unsubscribe();

```

## API

### `new PromiseObserver()`

Create new PromiseObserver.

### `subscribe(promise: Promise, callback: Callback, unsubscribedCallback?: Callback): Promise`

Subscribe to `promise`. After the `promise` is resolved the `callback` will be called with either

`{ value: null; error: Error; }` or `{ value: T; error: null; }` argument. Optional `unsubscribedCallback` will be called for unsubscribed promises. Return the same promise.

### `unsubscribe(): void`

Unsubscribe from subscribed Promise

### `isSubscribed(): boolean`

Is observer awaiting for any promise result?

### `PromiseObserver.WARN_ON_ERROR`

Static property. When true will warn in console on each rejection. Useful for debugging

## License

Pietile Promise Observer is MIT License.