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https://github.com/sindresorhus/p-reflect
Make a promise always fulfill with its actual fulfillment value or rejection reason
https://github.com/sindresorhus/p-reflect
Last synced: about 1 month ago
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Make a promise always fulfill with its actual fulfillment value or rejection reason
- Host: GitHub
- URL: https://github.com/sindresorhus/p-reflect
- Owner: sindresorhus
- License: mit
- Created: 2016-11-26T05:19:12.000Z (almost 8 years ago)
- Default Branch: main
- Last Pushed: 2023-01-29T20:26:47.000Z (almost 2 years ago)
- Last Synced: 2024-05-19T14:04:48.136Z (6 months ago)
- Language: JavaScript
- Size: 13.7 KB
- Stars: 51
- Watchers: 7
- Forks: 8
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
- License: license
Awesome Lists containing this project
- promise-fun - p-reflect
README
# p-reflect
> Make a promise always fulfill with its actual fulfillment value or rejection reason
Useful when you want a promise to fulfill no matter what and would rather handle the actual state afterwards.
## Install
```
$ npm install p-reflect
```
## Usage
Here, `Promise.all` would normally fail early because one of the promises rejects, but by using `p-reflect`, we can ignore the rejection and handle it later on.
```js
import pReflect from 'p-reflect';
const promises = [
getPromise(),
getPromiseThatRejects(),
getPromise()
];
const results = await Promise.all(promises.map(pReflect));
console.log(results);
/*
[
{
status: 'fulfilled',
value: '🦄'
isFulfilled: true,
isRejected: false
},
{
status: 'rejected',
reason: [Error: 👹]
isFulfilled: false,
isRejected: true
},
{
status: 'fulfilled',
value: '🐴'
isFulfilled: true,
isRejected: false
}
]
*/
const resolvedString = results
.filter(result => result.isFulfilled)
.map(result => result.value)
.join('');
console.log(resolvedString);
//=> '🦄🐴'
```
The above is just an example. Use [`p-settle`](https://github.com/sindresorhus/p-settle) if you need exactly that.
## API
### pReflect(promise)
Returns a `Promise`.
The object has the following properties:
- `status` *(`'fulfilled'` or `'rejected'`, depending on how the promise resolved)*
- `value` or `reason` *(Depending on whether the promise fulfilled or rejected)*
- `isFulfilled`
- `isRejected`
#### promise
Type: `Promise`
A promise to reflect upon.
### isFulfilled(object)
This is a type guard for TypeScript users.
Returns `true` if the object has the property `value`, `false` otherwise.
This is useful since `await pReflect(promise)` always returns a `PromiseResult`. This function can be used to determine whether `PromiseResult` is `PromiseFulfilledResult` or `PromiseRejectedResult`.
This is a workaround for [microsoft/TypeScript#32399](https://github.com/microsoft/TypeScript/issues/32399)
- reference documentation [Using type predicates](https://www.typescriptlang.org/docs/handbook/2/narrowing.html)
### isRejected(object)
This is a type guard for TypeScript users.
Returns `true` if the object has the property `reason`, `false` otherwise.
This is useful since `await pReflect(promise)` always returns a `PromiseResult`. This function can be used to determine whether `PromiseResult` is `PromiseRejectedResult` or `PromiseFulfilledResult`.
## Related
- [p-settle](https://github.com/sindresorhus/p-settle) - Settle promises concurrently and get their fulfillment value or rejection reason
- [More…](https://github.com/sindresorhus/promise-fun)