promise-effects
v2.1.0
Published
Promise effects for advanced use cases like retry, timeout, observation over promises.
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Promise Effects
Fully typed promise effects to play with async handlers in a pleasent way.
| Effect | Desc | |-----------------------------------|-------------------------------------------------------| | retryPromise | Converts a promise creator to repetitive | | wait | Creates a promise to resolve for the given time long. | | observePromise | Creates observable promises from the given promise | | timeout | Timeout example | | Polling | ⏱ Polling example | | Latest | ⏱ | | CancelablePromise | ⏱ |
Usage
Install package
npm install promise-effects
Import module
import { retryPromise } from 'promise-effects'
// or
import retryPromise from 'promise-effects/retryPromise'
Effects
RetryPromise
It's a high-order function that gives the capabilify of retry to a function that creates promise.
const repetitiveFetch = retryPromise(fetch, {
retry: 3,
onReconnecting: ({ attemptNumber }) => console.log(`Fetching has failed(${attemptNumber})... Retrying...`),
})
repetitiveFetch('https://www.mocky.io/v2/5185415ba171ea3a00704eed')
.then(resp=> resp.json())
.then(console.log)
.catch(() => console.log('Failed!'))
// > Fetching has failed(1)... Retrying...
// > Fetching has failed(2)... Retrying...
// > Fetching has failed(3)... Retrying...
// > Failed!
Options
| Option Name | Type |
|----------------|---------------------------------------------------------------------------------------------|
| onReconnecting | fn:({attemptNumber: number, remainingTries: number, error: Error})
|
| delay | number
|
| delay | { delay: number, factor: number, max?: number, min?: number }
|
| delay | fn: ({attemptNumber: number, remainingTries: number, error: Error}) => number | Promise
|
| shouldRetry | fn: ({attemptNumber: number, remainingTries: number, error: Error}) => booleaan |Promise<boolean>
|
| retry | number
|
observePromise
It wraps promises to observe the status. You can get if the promise fulfilled
, rejected
or pending
. It's beneficial on test purposes.
const observed = observePromise(fetch('http://google.com'))
console.log(observed.isPending()) // > true
console.log(observed.isRejected()) // > false
console.log(observed.isFulfilled()) // > false
console.log(observed.status) // > 'PENDING'
observed
.then(result=> {
console.log(observed.status) // > 'RESOLVED'
console.log(observed.isFulfilled()) // > true
})
.catch(() => {
console.log(observed.status) // > 'REJECTED'
console.log(observed.isRejected()) // > true
})
wait
Creates a promise to resolve for the given time long.
const printMessage = (count=0) =>
Promise.resolve()
.then(() => console.log(`You will see this message every second(${count})`))
.then(() => wait(1000).then(() => printMessage(count + 1)))
printMessage()
// > You will see this message every second(0)
// > You will see this message every second(1)
// > You will see this message every second(2)
// > You will see this message every second(3)
// > ...
timeout
You don't need an exclusive timeout function for timeout. Use wait
with ES Promise.race instead.
// fail in 1 sec
Promise.race([
fetch('https://www.mocky.io/v2/5185415ba171ea3a00704eed?mocky-delay=1200ms').then(res=> resp.json()),
wait(1000).then(()=> Promise.reject('Timeout!'))
])
// > Uncaught (in promise) Timeout!
// will mock response if the first request doesn't resolve in 1 sec
const result = await Promise.race([
fetch('https://www.mocky.io/v2/5185415ba171ea3a00704eed?mocky-delay=1200ms').then(res=> resp.json()),
wait(1000).then(()=> ({ hello: 'mock' }))
])
console.log(result)
// > { hello: 'mock' }
Changelog
All notable changes to this project will be documented in the changelog file.