get-iterator

Get the default iterator or async iterator for an iterable or async iterable

Reduce the boilerplate of extracting the iterator from an object when you don't know if the object is an (async) iterable or already an (async) iterator.

Install

1npm install get-iterator

Usage

1import { getIterator } from 'get-iterator'
2const input = [1, 2, 3]
3const it = getIterator(input)
4console.log(it.next()) // { done: false, value: 1 }
5console.log(it.next()) // { done: false, value: 2 }
6console.log(it.next()) // { done: false, value: 3 }
7console.log(it.next()) // { done: true, value: undefined }

Examples

Regular iterator from iterable:

1import { getIterator } from 'get-iterator'
2
3const input = [1, 2, 3]
4const iterable = {
5  [Symbol.iterator] () {
6    let i = 0
7    return {
8      next () {
9        const value = input[i++]
10        return { done: !value, value }
11      }
12    }
13  }
14}
15
16const it = getIterator(input)
17console.log(it.next()) // { done: false, value: 1 }
18console.log(it.next()) // { done: false, value: 2 }
19console.log(it.next()) // { done: false, value: 3 }
20console.log(it.next()) // { done: true, value: undefined }

Async iterator from iterable:

1import { getIterator } from 'get-iterator'
2
3const input = [1, 2, 3]
4const iterable = {
5  [Symbol.asyncIterator] () {
6    let i = 0
7    return {
8      async next () {
9        const value = await new Promise((resolve, reject) => {
10          setTimeout(() => resolve(input[i++]), 10)
11        })
12        return { done: !value, value }
13      }
14    }
15  }
16}
17
18const it = getIterator(iterable)
19console.log(await it.next()) // { done: false, value: 1 }
20console.log(await it.next()) // { done: false, value: 2 }
21console.log(await it.next()) // { done: false, value: 3 }
22console.log(await it.next()) // { done: true, value: undefined }

Already an iterator (probably):

1import { getIterator } from 'get-iterator'
2
3const input = [1, 2, 3]
4let i = 0
5const iterator = {
6  next () {
7    const value = input[i++]
8    return { done: !value, value }
9  }
10}
11
12const it = getIterator(iterator)
13console.log(it.next()) // { done: false, value: 1 }
14console.log(it.next()) // { done: false, value: 2 }
15console.log(it.next()) // { done: false, value: 3 }
16console.log(it.next()) // { done: true, value: undefined }

API

1import { getIterator } from 'get-iterator'

getIterator(obj)

Get the default iterator or async iterator for an Iterable. If obj is already an iterator (i.e. has a next function) return it, since it's probably already an iterator.

This function will throw if obj is not an iterable or iterator.

Parameters

Name	Type	Description
obj	Iterable|Iterator	The object to extract the iterator from (may be an iterator already).

Returns

Type	Description
Iterator	The result of calling obj[Symbol.iterator]() or obj[Symbol.asyncIterator]() or simply the passed obj if it is already an iterator.

Contribute

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

License

MIT © Alan Shaw