p-reflect
v3.1.0
Published
Make a promise always fulfill with its actual fulfillment value or rejection reason
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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.
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
if you need exactly that.
API
pReflect(promise)
Returns a Promise<Object>
.
The object has the following properties:
status
('fulfilled'
or'rejected'
, depending on how the promise resolved)value
orreason
(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
- reference documentation Using type predicates
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
.