abort overview

abort combinators: cancel requests via AbortController.

About AbortController compatibility

AbortController is an experimental technology defined in the current DOM specification.

Thus, it is not supported by old browsers (e.g. IE11) and Nodejs environments.

We suggest you to use a polyfill (check out the _setup.ts file in the test folder) like:

• abort-controller
• abortcontroller-polyfill

Warning: the merging logic had to be “reversed” because of the contravariant nature of Reader and because the execution of combinators is from right to left (function composition).

This leads to a “weird” behavior for which the signal provided when Req is run wins over the one set with the combinator.

So, for example, if we have:

const controller1 = new AbortController()
const controller2 = new AbortController()

const request = pipe(appy.get, withCancel(controller1))

request(['http://some.endpoint', { signal: controller2.signal }])

the request will be aborted only when controller2 calls the abort() method.

Added in v3.1.0

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Table of contents

• combinators
  • withCancel
  • withTimeout

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combinators

withCancel

Sets signal on Req in order to make request cancellable through AbortController.

Example:

import { request } from '@contactlab/appy'
import { withCancel } from '@contactlab/appy/combinators/abort'
import { isLeft } from 'fp-ts/Either'
import { pipe } from 'fp-ts/function'

const controller = new AbortController()

const requestWithCancel = pipe(request, withCancel(controller))
const users = requestWithCancel('https://reqres.in/api/users')

controller.abort()

users().then((result) => {
  assert.ok(isLeft(result))
})

Signature

export declare const withCancel: (controller: AbortController) => Combinator

Added in v3.1.0

withTimeout

Aborts the request if it does not respond within provided milliseconds.

Example:

import { request } from '@contactlab/appy'
import { withTimeout } from '@contactlab/appy/combinators/abort'
import { isLeft } from 'fp-ts/Either'
import { pipe } from 'fp-ts/function'

const requestWithTimeout = pipe(request, withTimeout(500))
const users = requestWithTimeout('https://reqres.in/api/users')

users().then((result) => {
  assert.ok(isLeft(result)) // <-- because timeout is really small
})

Signature

export declare const withTimeout: (millis: number) => <A>(req: Req<A>) => Req<A>

Added in v3.1.0