promise-effects

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
shouldRetry	`fn: ({attemptNumber: number, remainingTries: number, error: Error}) => booleaan
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.