fp-ts-iter

Functional async iterators for TypeScript, built on fp-ts.

Quick Start 

import { pipe } from 'fp-ts/function'
import * as AI from 'fp-ts-iter/AsyncIter'

const result = pipe(
  AI.fromIterable([1, 2, 3, 4, 5]),
  AI.map(x => x * 2),
  AI.filter(x => x > 4),
  AI.toArray
)

console.log(await result()) // [6, 8, 10]

Error Handling 

import * as AIE from 'fp-ts-iter/AsyncIterEither'

const parseNumber = (s: string) => 
  isNaN(+s) ? AIE.left('Invalid') : AIE.right(+s)

const result = pipe(
  AIE.of('1', '2', 'bad', '4'),
  AIE.chain(parseNumber),
  AIE.toArray
)
// Returns E.left('Invalid') on first error

Types

  • AsyncIter<A> - Lazy async iterators
  • AsyncIterEither<E, A> - Async iterators with error handling

Documentation