abortable-iterator

abortable-iterator

Make any iterator or iterable abortable via an AbortSignal

The AbortController is used in the fetch API to abort in flight requests from, for example, a timeout or user action. The same concept is used here to halt iteration of an async iterator.

Install

npm install abortable-iterator

Usage

const abortable = require('abortable-iterator')
const AbortController = require('abort-controller')

// An example function that creates an async iterator that yields an increasing
// number every x milliseconds and NEVER ENDS!
const asyncCounter = async function * (start, delay) {
  let i = start
  while (true) {
    yield new Promise(resolve => setTimeout(() => resolve(i++), delay))
  }
}

// Create a counter that'll yield numbers from 0 upwards every second
const everySecond = asyncCounter(0, 1000)

// Make everySecond abortable!
const controller = new AbortController()
const abortableEverySecond = abortable(everySecond, controller.signal)

// Abort after 5 seconds
setTimeout(() => controller.abort(), 5000)

try {
  // Start the iteration, which will throw after 5 seconds when it is aborted
  for await (const n of abortableEverySecond) {
    console.log(n)
  }
} catch (err) {
  if (err.code === 'ERR_ABORTED') {
    // Expected - all ok :D
  } else {
    throw err
  }
}

API

const abortable = require('abortable-iterator')

• abortable(source, signal, [options])
• abortable(source, signals)
• abortable.source(source, signal, [options])
• abortable.source(source, signals)
• abortable.sink(sink, signal, [options])
• abortable.sink(sink, signals)
• abortable.transform(transform, signal, [options])
• abortable.transform(transform, signals)
• abortable.duplex(duplex, signal, [options])
• abortable.duplex(duplex, signals)

abortable(source, signal, [options])

(alias for abortable.source(source, signal, [options]))

Make any iterator or iterable abortable via an AbortSignal.

Parameters

Name	Type	Description
source	Iterable|Iterator	The iterator or iterable object to make abortable
signal	AbortSignal	Signal obtained from AbortController.signal which is used to abort the iterator.
options	Object	(optional) options
options.onAbort	Function	An (async) function called when the iterator is being aborted, before the abort error is thrown. Default null
options.abortMessage	String	The message that the error will have if the iterator is aborted. Default "The operation was aborted"
options.abortCode	String|Number	The value assigned to the code property of the error that is thrown if the iterator is aborted. Default "ABORT_ERR"
options.returnOnAbort	Boolean	Instead of throwing the abort error, just return from iterating over the source stream.
options.onReturnError	Function	When a generator is aborted, we call .return on it - if this function errors the error value will be passed to the .onReturnError callback if passed. Default null

Returns

Type	Description
Iterable	An iterator that wraps the passed source parameter that makes it abortable via the passed signal parameter.

The returned iterator will throw an AbortError when it is aborted that has a type with the value aborted and code property with the value ABORT_ERR by default.

abortable(source, signals)

(alias for abortable.source(source, signals))

Make any iterator or iterable abortable via any one of the passed AbortSignal's.

Parameters

Name	Type	Description
source	Iterable|Iterator	The iterator or iterable object to make abortable
signals	Array<{ signal, [options] }>	An array of objects with signal and optional options properties. See above docs for expected values for these two properties.

Returns

Type	Description
Iterator	An iterator that wraps the passed source parameter that makes it abortable via the passed signal parameters.

The returned iterator will throw an AbortError when it is aborted on any one of the passed abort signals. The error object has a type with the value aborted and code property with the value ABORT_ERR by default.

abortable.sink(sink, signal, [options])

The same as abortable.source except this makes the passed sink abortable. Returns a new sink that wraps the passed sink and makes it abortable via the passed signal parameter.

abortable.sink(sink, signals)

The same as abortable.source except this makes the passed sink abortable via any one of the passed AbortSignal's. Returns a new sink that wraps the passed sink and makes it abortable via the passed signal parameters.

abortable.transform(transform, signal, [options])

The same as abortable.source except this makes the passed transform abortable. Returns a new transform that wraps the passed transform and makes it abortable via the passed signal parameter.

abortable.transform(transform, signals)

The same as abortable.source except this makes the passed transform abortable via any one of the passed AbortSignal's. Returns a new transform that wraps the passed transform and makes it abortable via the passed signal parameters.

abortable.duplex(duplex, signal, [options])

The same as abortable.source except this makes the passed duplex abortable. Returns a new duplex that wraps the passed duplex and makes it abortable via the passed signal parameter.

Note that this will abort both sides of the duplex. Use duplex.sink = abortable.sink(duplex.sink) or duplex.source = abortable.source(duplex.source) to abort just the sink or the source.

abortable.duplex(duplex, signals)

The same as abortable.source except this makes the passed duplex abortable via any one of the passed AbortSignal's. Returns a new duplex that wraps the passed duplex and makes it abortable via the passed signal parameters.

Note that this will abort both sides of the duplex. Use duplex.sink = abortable.sink(duplex.sink) or duplex.source = abortable.source(duplex.source) to abort just the sink or the source.

Related

• it-pipe Utility to "pipe" async iterables together

Contribute

Feel free to dive in! Open an issue or submit PRs.

License

MIT © Alan Shaw