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https://github.com/jsr-core/iterutil

Iterator / AsyncIterator utility pack for JavaScript / TypeScript
https://github.com/jsr-core/iterutil

asynciterator iterator javascript jsr typescript

Last synced: 18 days ago
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Iterator / AsyncIterator utility pack for JavaScript / TypeScript

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# iterutil



[![jsr](https://jsr.io/badges/@core/iterutil)](https://jsr.io/@core/iterutil)

[![test](https://github.com/jsr-core/iterutil/workflows/Test/badge.svg)](https://github.com/jsr-core/iterutil/actions?query=workflow%3ATest)

[![codecov](https://codecov.io/github/jsr-core/iterutil/graph/badge.svg?token=pfbLRGU5AM)](https://codecov.io/github/jsr-core/iterutil)



Iterator / AsyncIterator utility pack for JavaScript and TypeScript. Each module

is designed to work independently, avoiding internal inter-dependencies as much

as possible.



## Usage



To apply single operation to an iterable, use modules under the root.



```ts

import { map } from "@core/iterutil/map";



const iter = map([1, 2, 3], (v) => v * 2);

console.log(Array.from(iter)); // [2, 4, 6]

```



To apply single asynchronous operation to an (async) iterable, use modules under

the `async` submodule.



```ts

import { map } from "@core/iterutil/async/map";



const iter = map([1, 2, 3], (v) => Promise.resolve(v * 2));

console.log(await Array.fromAsync(iter)); // [2, 4, 6]

```



To apply multiple operations to an iterable, use the modules under the `pipe`

submodule with the [@core/pipe] package.



```ts

import { pipe } from "@core/pipe";

import { cycle } from "@core/iterutil/pipe/cycle";

import { filter } from "@core/iterutil/pipe/filter";

import { map } from "@core/iterutil/pipe/map";

import { take } from "@core/iterutil/pipe/take";



const iter = pipe(

  [1, 2, 3],

  map((v) => v * 2),

  cycle,

  take(10),

  filter((v) => v % 2 === 0),

);

console.log(Array.from(iter)); // [2, 4, 6, 2, 4, 6, 2, 4, 6, 2]

```



To apply multiple asynchronous operations to an (async) iterable, use the

modules under the `pipe/async` submodule with the [@core/pipe] package.



```ts

import { pipe } from "@core/pipe";

import { cycle } from "@core/iterutil/pipe/async/cycle";

import { filter } from "@core/iterutil/pipe/async/filter";

import { map } from "@core/iterutil/pipe/async/map";

import { take } from "@core/iterutil/pipe/async/take";



const iter = pipe(

  [1, 2, 3],

  map((v) => Promise.resolve(v * 2)),

  cycle,

  take(10),

  filter((v) => Promise.resolve(v % 2 === 0)),

);

console.log(await Array.fromAsync(iter)); // [2, 4, 6, 2, 4, 6, 2, 4, 6, 2]

```



[@core/pipe]: https://jsr.io/@core/pipe



### chain



Chains multiple iterables together.



```ts

import { chain } from "@core/iterutil/chain";



const iter = chain([1, 2], ["a", "b"], [true, false]);

console.log(Array.from(iter)); // [1, 2, "a", "b", true, false]

```



```ts

import { chain } from "@core/iterutil/async/chain";



const iter = chain([1, 2], ["a", "b"], [true, false]);

console.log(await Array.fromAsync(iter)); // [1, 2, "a", "b", true, false]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { chain } from "@core/iterutil/pipe/chain";



const iter = pipe(

  [1, 2],

  chain(["a", "b"], [true, false]),

);

console.log(Array.from(iter)); // [1, 2, "a", "b", true, false]

```



```ts

import { pipe } from "@core/pipe";

import { chain } from "@core/iterutil/pipe/async/chain";



const iter = pipe(

  [1, 2],

  chain(["a", "b"], [true, false]),

);

console.log(await Array.fromAsync(iter)); // [1, 2, "a", "b", true, false]

```



### chunked



Chunks an iterable into arrays of a given size.



```ts

import { chunked } from "@core/iterutil/chunked";



const iter = chunked([1, 2, 3, 4, 5], 2);

console.log(Array.from(iter)); // [[1, 2], [3, 4], [5]]

```



```ts

import { chunked } from "@core/iterutil/async/chunked";



const iter = chunked([1, 2, 3, 4, 5], 2);

console.log(await Array.fromAsync(iter)); // [[1, 2], [3, 4], [5]]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { chunked } from "@core/iterutil/pipe/chunked";



const iter = pipe(

  [1, 2, 3, 4, 5],

  chunked(2),

);

console.log(Array.from(iter)); // [[1, 2], [3, 4], [5]]

```



```ts

import { pipe } from "@core/pipe";

import { chunked } from "@core/iterutil/pipe/async/chunked";



const iter = pipe(

  [1, 2, 3, 4, 5],

  chunked(2),

);

console.log(await Array.fromAsync(iter)); // [[1, 2], [3, 4], [5]]

```



### compact



Removes all nullish (`null` or `undefined`) values from an iterable.



```ts

import { compact } from "@core/iterutil/compact";



const iter = compact([1, undefined, 2, null, 3]);

console.log(Array.from(iter)); // [1, 2, 3]

```



```ts

import { compact } from "@core/iterutil/async/compact";



const iter = compact([1, undefined, 2, null, 3]);

console.log(await Array.fromAsync(iter)); // [1, 2, 3]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { compact } from "@core/iterutil/pipe/compact";



const iter = pipe(

  [1, undefined, 2, null, 3],

  compact,

);

console.log(Array.from(iter)); // [1, 2, 3]

```



```ts

import { pipe } from "@core/pipe";

import { compact } from "@core/iterutil/pipe/async/compact";



const iter = pipe(

  [1, undefined, 2, null, 3],

  compact,

);

console.log(await Array.fromAsync(iter)); // [1, 2, 3]

```



### compress



Compresses an iterable by selecting elements using a selector iterable.



```ts

import { compress } from "@core/iterutil/compress";



const iter = compress(

  [1, 2, 3, 4, 5],

  [true, false, true, false, true],

);

console.log(Array.from(iter)); // [1, 3, 5]

```



```ts

import { compress } from "@core/iterutil/async/compress";



const iter = compress(

  [1, 2, 3, 4, 5],

  [true, false, true, false, true],

);

console.log(await Array.fromAsync(iter)); // [1, 3, 5]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { compress } from "@core/iterutil/pipe/compress";



const iter = pipe(

  [1, 2, 3, 4, 5],

  compress([true, false, true, false, true]),

);

console.log(Array.from(iter)); // [1, 3, 5]

```



```ts

import { pipe } from "@core/pipe";

import { compress } from "@core/iterutil/pipe/async/compress";



const iter = pipe(

  [1, 2, 3, 4, 5],

  compress([true, false, true, false, true]),

);

console.log(await Array.fromAsync(iter)); // [1, 3, 5]

```



### count



Generates an infinite sequence of numbers starting from `start` with a step of

`step`.



```ts

import { count } from "@core/iterutil/count";

import { take } from "@core/iterutil/take";



const iter = count(1, 2);

console.log(Array.from(take(iter, 5))); // [1, 3, 5, 7, 9]

```



### cycle



Returns an infinite iterable that cycles through the given iterable.



```ts

import { cycle } from "@core/iterutil/cycle";

import { take } from "@core/iterutil/take";



const iter = cycle([1, 2, 3]);

console.log(Array.from(take(iter, 5))); // [1, 2, 3, 1, 2]

```



```ts

import { cycle } from "@core/iterutil/async/cycle";

import { take } from "@core/iterutil/async/take";



const iter = cycle([1, 2, 3]);

console.log(await Array.fromAsync(take(iter, 5))); // [1, 2, 3, 1, 2]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { cycle } from "@core/iterutil/pipe/cycle";

import { take } from "@core/iterutil/pipe/take";



const iter = pipe(

  [1, 2, 3],

  cycle,

  take(5),

);

console.log(Array.from(iter)); // [1, 2, 3, 1, 2]

```



```ts

import { pipe } from "@core/pipe";

import { cycle } from "@core/iterutil/pipe/async/cycle";

import { take } from "@core/iterutil/pipe/async/take";



const iter = pipe(

  [1, 2, 3],

  cycle,

  take(5),

);

console.log(await Array.fromAsync(iter)); // [1, 2, 3, 1, 2]

```



### drop



Drops the first `limit` items from the iterable.



```ts

import { drop } from "@core/iterutil/drop";



const iter = drop([1, 2, 3, 4, 5], 2);

console.log(Array.from(iter)); // [3, 4, 5]

```



```ts

import { drop } from "@core/iterutil/async/drop";



const iter = drop([1, 2, 3, 4, 5], 2);

console.log(await Array.fromAsync(iter)); // [3, 4, 5]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { drop } from "@core/iterutil/pipe/drop";



const iter = pipe(

  [1, 2, 3, 4, 5],

  drop(2),

);

console.log(Array.from(iter)); // [3, 4, 5]

```



```ts

import { pipe } from "@core/pipe";

import { drop } from "@core/iterutil/pipe/async/drop";



const iter = pipe(

  [1, 2, 3, 4, 5],

  drop(2),

);

console.log(await Array.fromAsync(iter)); // [3, 4, 5]

```



### dropWhile



Drops elements from the iterable while the predicate returns true.



```ts

import { dropWhile } from "@core/iterutil/drop-while";



const iter = dropWhile(

  [1, 2, 3, 4, 5],

  (v) => v < 3,

);

console.log(Array.from(iter)); // [3, 4, 5]

```



```ts

import { dropWhile } from "@core/iterutil/async/drop-while";



const iter = dropWhile(

  [1, 2, 3, 4, 5],

  (v) => v < 3,

);

console.log(await Array.fromAsync(iter)); // [3, 4, 5]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { dropWhile } from "@core/iterutil/pipe/drop-while";



const iter = pipe(

  [1, 2, 3, 4, 5],

  dropWhile((v) => v < 3),

);

console.log(Array.from(iter)); // [3, 4, 5]

```



```ts

import { pipe } from "@core/pipe";

import { dropWhile } from "@core/iterutil/pipe/async/drop-while";



const iter = pipe(

  [1, 2, 3, 4, 5],

  dropWhile((v) => v < 3),

);

console.log(await Array.fromAsync(iter)); // [3, 4, 5]

```



### enumerate



Enumerates an iterable.



```ts

import { enumerate } from "@core/iterutil/enumerate";



const iter = enumerate(["a", "b", "c"]);

console.log(Array.from(iter)); // [[0, "a"], [1, "b"], [2, "c"]]

```



```ts

import { enumerate } from "@core/iterutil/async/enumerate";



const iter = enumerate(["a", "b", "c"]);

console.log(await Array.fromAsync(iter)); // [[0, "a"], [1, "b"], [2, "c"]]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { enumerate } from "@core/iterutil/pipe/enumerate";



const iter = pipe(["a", "b", "c"], enumerate);

console.log(Array.from(iter)); // [[0, "a"], [1, "b"], [2, "c"]]

```



```ts

import { pipe } from "@core/pipe";

import { enumerate } from "@core/iterutil/pipe/async/enumerate";



const iter = pipe(["a", "b", "c"], enumerate);

console.log(await Array.fromAsync(iter)); // [[0, "a"], [1, "b"], [2, "c"]]

```



### every



Returns true if every element in the iterable satisfies the provided testing

function.



```ts

import { every } from "@core/iterutil/every";



console.log(every([1, 2, 3], (v) => v > 0)); // true

console.log(every([1, 2, 3], (v) => v > 1)); // false

```



```ts

import { every } from "@core/iterutil/async/every";



console.log(await every([1, 2, 3], (v) => v > 0)); // true

console.log(await every([1, 2, 3], (v) => v > 1)); // false

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { every } from "@core/iterutil/pipe/every";



console.log(pipe([1, 2, 3], every((v) => v > 0))); // true

console.log(pipe([1, 2, 3], every((v) => v > 1))); // false

```



```ts

import { pipe } from "@core/pipe";

import { every } from "@core/iterutil/pipe/async/every";



console.log(await pipe([1, 2, 3], every((v) => v > 0))); // true

console.log(await pipe([1, 2, 3], every((v) => v > 1))); // false

```



### filter



Filters an iterable based on a function.



```ts

import { filter } from "@core/iterutil/filter";



const iter = filter(

  [1, 2, 3, 4, 5],

  (v) => v % 2 === 0,

);

console.log(Array.from(iter)); // [2, 4]

```



```ts

import { filter } from "@core/iterutil/async/filter";



const iter = filter(

  [1, 2, 3, 4, 5],

  (v) => v % 2 === 0,

);

console.log(await Array.fromAsync(iter)); // [2, 4]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { filter } from "@core/iterutil/pipe/filter";



const iter = pipe(

  [1, 2, 3, 4, 5],

  filter((v) => v % 2 === 0),

);

console.log(Array.from(iter)); // [2, 4]

```



```ts

import { pipe } from "@core/pipe";

import { filter } from "@core/iterutil/pipe/async/filter";



const iter = pipe(

  [1, 2, 3, 4, 5],

  filter((v) => v % 2 === 0),

);

console.log(await Array.fromAsync(iter)); // [2, 4]

```



### find



Returns the first element in the iterable that satisfies the provided testing

function. Otherwise, undefined is returned.



```ts

import { find } from "@core/iterutil/find";



const value = find(

  [1, 2, 3, 4, 5],

  (v) => v % 2 === 0,

);

console.log(value); // 2

```



```ts

import { find } from "@core/iterutil/async/find";



const value = await find(

  [1, 2, 3, 4, 5],

  (v) => v % 2 === 0,

);

console.log(value); // 2

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { find } from "@core/iterutil/pipe/find";



const value = pipe(

  [1, 2, 3, 4, 5],

  find((v) => v % 2 === 0),

);

console.log(value); // 2

```



```ts

import { pipe } from "@core/pipe";

import { find } from "@core/iterutil/pipe/async/find";



const value = await pipe(

  [1, 2, 3, 4, 5],

  find((v) => v % 2 === 0),

);

console.log(value); // 2

```



### first



Returns the first element of an iterable. If the iterable is empty, returns

`undefined`.



```ts

import { first } from "@core/iterutil/first";



const result = first([1, 2, 3]);

console.log(result); // 1

```



```ts

import { first } from "@core/iterutil/async/first";



const result = await first([1, 2, 3]);

console.log(result); // 1

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { first } from "@core/iterutil/pipe/first";



const result = pipe([1, 2, 3], first);

console.log(result); // 1

```



```ts

import { pipe } from "@core/pipe";

import { first } from "@core/iterutil/pipe/async/first";



const result = await pipe([1, 2, 3], first);

console.log(result); // 1

```



### flatMap



Maps each value in an iterable to an iterable, then flattens the result.



```ts

import { flatMap } from "@core/iterutil/flat-map";



const iter = flatMap(

  [1, 2, 3],

  (v) => [v, v],

);

console.log(Array.from(iter)); // [1, 1, 2, 2, 3, 3]

```



```ts

import { flatMap } from "@core/iterutil/async/flat-map";



const iter = flatMap(

  [1, 2, 3],

  (v) => [v, v],

);

console.log(await Array.fromAsync(iter)); // [1, 1, 2, 2, 3, 3]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { flatMap } from "@core/iterutil/pipe/flat-map";



const iter = pipe(

  [1, 2, 3],

  flatMap((v) => [v, v]),

);

console.log(Array.from(iter)); // [1, 1, 2, 2, 3, 3]

```



```ts

import { pipe } from "@core/pipe";

import { flatMap } from "@core/iterutil/pipe/async/flat-map";



const iter = pipe(

  [1, 2, 3],

  flatMap((v) => [v, v]),

);

console.log(await Array.fromAsync(iter)); // [1, 1, 2, 2, 3, 3]

```



### flatten



Flattens an iterable of iterables into a single iterable.



```ts

import { flatten } from "@core/iterutil/flatten";



const iter = flatten([[1, 2], [3, 4], [5]]);

console.log(Array.from(iter)); // [1, 2, 3, 4, 5]

```



```ts

import { flatten } from "@core/iterutil/async/flatten";



const iter = flatten([[1, 2], [3, 4], [5]]);

console.log(await Array.fromAsync(iter)); // [1, 2, 3, 4, 5]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { flatten } from "@core/iterutil/pipe/flatten";



const iter = pipe(

  [[1, 2], [3, 4], [5]],

  flatten,

);

console.log(Array.from(iter)); // [1, 2, 3, 4, 5]

```



```ts

import { pipe } from "@core/pipe";

import { flatten } from "@core/iterutil/pipe/async/flatten";



const iter = pipe(

  [[1, 2], [3, 4], [5]],

  flatten,

);

console.log(await Array.fromAsync(iter)); // [1, 2, 3, 4, 5]

```



### forEach



Calls a function for each value in an iterable.



```ts

import { forEach } from "@core/iterutil/for-each";

forEach([1, 2, 3], (v) => console.log(v));

// 1

// 2

// 3

```



```ts

import { forEach } from "@core/iterutil/async/for-each";

await forEach([1, 2, 3], (v) => console.log(v));

// 1

// 2

// 3

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { forEach } from "@core/iterutil/pipe/for-each";

pipe(

  [1, 2, 3],

  forEach((v) => console.log(v)),

);

// 1

// 2

// 3

```



```ts

import { pipe } from "@core/pipe";

import { forEach } from "@core/iterutil/pipe/async/for-each";

await pipe(

  [1, 2, 3],

  forEach((v) => console.log(v)),

);

// 1

// 2

// 3

```



### iter



Converts an iterable to an iterator.



```ts

import { iter } from "@core/iterutil/iter";



const it = iter([1, 2, 3, 4, 5]);

console.log(it.next()); // { value: 1, done: false }

console.log(it.next()); // { value: 2, done: false }



for (const value of it) {

  console.log(value);

}

// 3

// 4

// 5

```



```ts

import { iter } from "@core/iterutil/async/iter";



const it = iter([1, 2, 3, 4, 5]);

console.log(await it.next()); // { value: 1, done: false }

console.log(await it.next()); // { value: 2, done: false }



for await (const value of it) {

  console.log(value);

}

// 3

// 4

// 5

```



### last



Returns the last element of an iterable.



```ts

import { last } from "@core/iterutil/last";



console.log(last([1, 2, 3])); // 3

console.log(last([])); // undefined

```



```ts

import { last } from "@core/iterutil/async/last";



console.log(await last([1, 2, 3])); // 3

console.log(await last([])); // undefined

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { last } from "@core/iterutil/pipe/last";



console.log(pipe([1, 2, 3], last)); // 3

console.log(pipe([], last)); // undefined

```



```ts

import { pipe } from "@core/pipe";

import { last } from "@core/iterutil/pipe/async/last";



console.log(await pipe([1, 2, 3], last)); // 3

console.log(await pipe([], last)); // undefined

```



### map



Maps an iterable with a function.



```ts

import { map } from "@core/iterutil/map";



const iter = map(

  [1, 2, 3],

  (v) => v * 2,

);

console.log(Array.from(iter)); // [2, 4, 6]

```



```ts

import { map } from "@core/iterutil/async/map";



const iter = map(

  [1, 2, 3],

  (v) => v * 2,

);

console.log(await Array.fromAsync(iter)); // [2, 4, 6]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { map } from "@core/iterutil/pipe/map";



const iter = pipe(

  [1, 2, 3],

  map((v) => v * 2),

);

console.log(Array.from(iter)); // [2, 4, 6]

```



```ts

import { pipe } from "@core/pipe";

import { map } from "@core/iterutil/pipe/async/map";



const iter = pipe(

  [1, 2, 3],

  map((v) => v * 2),

);

console.log(await Array.fromAsync(iter)); // [2, 4, 6]

```



### nth



Returns the n-th element of an iterable. If the length of the iterable is less,

returns `undefined`.



```ts

import { nth } from "@core/iterutil/nth";



const result = nth([1, 2, 3], 1);

console.log(result); // 2

```



```ts

import { nth } from "@core/iterutil/async/nth";



const result = await nth([1, 2, 3], 1);

console.log(result); // 2

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { nth } from "@core/iterutil/pipe/nth";



const result = pipe([1, 2, 3], nth(1));

console.log(result); // 2

```



```ts

import { pipe } from "@core/pipe";

import { nth } from "@core/iterutil/pipe/async/nth";



const result = await pipe([1, 2, 3], nth(1));

console.log(result); // 2

```



### pairwise



Returns an iterable that pairs adjacent elements from the input iterable.



```ts

import { pairwise } from "@core/iterutil/pairwise";



const iter = pairwise([1, 2, 3, 4, 5]);

console.log(Array.from(iter)); // [[1, 2], [2, 3], [3, 4], [4, 5]]

```



```ts

import { pairwise } from "@core/iterutil/async/pairwise";



const iter = pairwise([1, 2, 3, 4, 5]);

console.log(await Array.fromAsync(iter)); // [[1, 2], [2, 3], [3, 4], [4, 5]]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { pairwise } from "@core/iterutil/pipe/pairwise";



const iter = pipe(

  [1, 2, 3, 4, 5],

  pairwise,

);

console.log(Array.from(iter)); // [[1, 2], [2, 3], [3, 4], [4, 5]]

```



```ts

import { pipe } from "@core/pipe";

import { pairwise } from "@core/iterutil/pipe/async/pairwise";



const iter = pipe(

  [1, 2, 3, 4, 5],

  pairwise,

);

console.log(await Array.fromAsync(iter)); // [[1, 2], [2, 3], [3, 4], [4, 5]]

```



### partition



Partitions an iterable into two arrays based on a selector function.



```ts

import { partition } from "@core/iterutil/partition";



const [even, odd] = partition(

  [1, 2, 3, 4, 5],

  (v) => v % 2 === 0,

);

console.log(even); // [2, 4]

console.log(odd); // [1, 3, 5]

```



```ts

import { partition } from "@core/iterutil/async/partition";



const [even, odd] = await partition(

  [1, 2, 3, 4, 5],

  (v) => v % 2 === 0,

);

console.log(even); // [2, 4]

console.log(odd); // [1, 3, 5]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { partition } from "@core/iterutil/pipe/partition";



const [even, odd] = pipe(

  [1, 2, 3, 4, 5],

  partition((v) => v % 2 === 0),

);

console.log(even); // [2, 4]

console.log(odd); // [1, 3, 5]

```



```ts

import { pipe } from "@core/pipe";

import { partition } from "@core/iterutil/pipe/async/partition";



const [even, odd] = await pipe(

  [1, 2, 3, 4, 5],

  partition((v) => v % 2 === 0),

);

console.log(even); // [2, 4]

console.log(odd); // [1, 3, 5]

```



### range



Generates a range of numbers.



```ts

import { range } from "@core/iterutil/range";



console.log(Array.from(range(1, 3))); // [1, 2, 3]

console.log(Array.from(range(1, 6, 2))); // [1, 3, 5]

```



### reduce



Reduces an iterable into a single value.



```ts

import { reduce } from "@core/iterutil/reduce";



const sum = reduce(

  [1, 2, 3, 4, 5],

  (acc, v) => acc + v,

);

console.log(sum); // 15



const joined = reduce(

  [1, 2, 3, 4, 5],

  (acc, v) => acc + v,

  "",

);

console.log(joined); // 12345

```



```ts

import { reduce } from "@core/iterutil/async/reduce";



const sum = await reduce(

  [1, 2, 3, 4, 5],

  (acc, v) => acc + v,

);

console.log(sum); // 15



const joined = await reduce(

  [1, 2, 3, 4, 5],

  (acc, v) => acc + v,

  "",

);

console.log(joined); // 12345

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { reduce } from "@core/iterutil/pipe/reduce";



const sum = pipe(

  [1, 2, 3, 4, 5],

  reduce((acc, v) => acc + v),

);

console.log(sum); // 15



const joined = pipe(

  [1, 2, 3, 4, 5],

  reduce((acc, v) => acc + v, ""),

);

console.log(joined); // 12345

```



```ts

import { pipe } from "@core/pipe";

import { reduce } from "@core/iterutil/pipe/async/reduce";



const sum = await pipe(

  [1, 2, 3, 4, 5],

  reduce((acc, v) => acc + v),

);

console.log(sum); // 15



const joined = await pipe(

  [1, 2, 3, 4, 5],

  reduce((acc, v) => acc + v, ""),

);

console.log(joined); // 12345

```



### repeat



Returns an finite iterable that repeats through the given iterable.



```ts

import { repeat } from "@core/iterutil/repeat";



const iter = repeat([1, 2, 3], 2);

console.log(Array.from(iter)); // [1, 2, 3, 1, 2, 3]

```



```ts

import { repeat } from "@core/iterutil/async/repeat";



const iter = repeat([1, 2, 3], 2);

console.log(await Array.fromAsync(iter)); // [1, 2, 3, 1, 2, 3]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { repeat } from "@core/iterutil/pipe/repeat";



const iter = pipe(

  [1, 2, 3],

  repeat(2),

);

console.log(Array.from(iter)); // [1, 2, 3, 1, 2, 3]

```



```ts

import { pipe } from "@core/pipe";

import { repeat } from "@core/iterutil/pipe/async/repeat";



const iter = pipe(

  [1, 2, 3],

  repeat(2),

);

console.log(await Array.fromAsync(iter)); // [1, 2, 3, 1, 2, 3]

```



### repeatable



Transform an async iterable into a repeatable async iterable. It caches the

values of the original iterable so that it can be replayed. Useful for replaying

the costly async iterable.



```ts

import { repeatable } from "@core/iterutil/async/repeatable";

import { assertEquals } from "@std/assert";



const origin = (async function* () {

  yield 1;

  yield 2;

  yield 3;

})();

const iter = repeatable(origin);

assertEquals(await Array.fromAsync(iter), [1, 2, 3]);

assertEquals(await Array.fromAsync(iter), [1, 2, 3]); // iter can be replayed

assertEquals(await Array.fromAsync(origin), []); // origin is already consumed

```



### some



Returns true if at least one element in the iterable satisfies the provided



```ts

import { some } from "@core/iterutil/some";



console.log(some([1, 2, 3], (v) => v % 2 === 0)); // true

console.log(some([1, 3, 5], (v) => v % 2 === 0)); // false

```



```ts

import { some } from "@core/iterutil/async/some";



console.log(await some([1, 2, 3], (v) => v % 2 === 0)); // true

console.log(await some([1, 3, 5], (v) => v % 2 === 0)); // false

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { some } from "@core/iterutil/pipe/some";



console.log(pipe([1, 2, 3], some((v) => v % 2 === 0))); // true

console.log(pipe([1, 3, 5], some((v) => v % 2 === 0))); // false

```



```ts

import { pipe } from "@core/pipe";

import { some } from "@core/iterutil/pipe/async/some";



console.log(await pipe([1, 2, 3], some((v) => v % 2 === 0))); // true

console.log(await pipe([1, 3, 5], some((v) => v % 2 === 0))); // false

```



### take



Takes the first `limit` items from the iterable.



```ts

import { take } from "@core/iterutil/take";



const iter = take([1, 2, 3, 4, 5], 2);

console.log(Array.from(iter)); // [1, 2]

```



```ts

import { take } from "@core/iterutil/async/take";



const iter = take([1, 2, 3, 4, 5], 2);

console.log(await Array.fromAsync(iter)); // [1, 2]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { take } from "@core/iterutil/pipe/take";



const iter = pipe(

  [1, 2, 3, 4, 5],

  take(2),

);

console.log(Array.from(iter)); // [1, 2]

```



```ts

import { pipe } from "@core/pipe";

import { take } from "@core/iterutil/pipe/async/take";



const iter = pipe(

  [1, 2, 3, 4, 5],

  take(2),

);

console.log(await Array.fromAsync(iter)); // [1, 2]

```



### takeWhile



Takes elements from the iterable while the predicate is true.



```ts

import { takeWhile } from "@core/iterutil/take-while";



const iter = takeWhile(

  [1, 2, 3, 4, 5],

  (v) => v < 4,

);

console.log(Array.from(iter)); // [1, 2, 3]

```



```ts

import { takeWhile } from "@core/iterutil/async/take-while";



const iter = takeWhile(

  [1, 2, 3, 4, 5],

  (v) => v < 4,

);

console.log(await Array.fromAsync(iter)); // [1, 2, 3]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { takeWhile } from "@core/iterutil/pipe/take-while";



const iter = pipe(

  [1, 2, 3, 4, 5],

  takeWhile((v) => v < 4),

);

console.log(Array.from(iter)); // [1, 2, 3]

```



```ts

import { pipe } from "@core/pipe";

import { takeWhile } from "@core/iterutil/pipe/async/take-while";



const iter = pipe(

  [1, 2, 3, 4, 5],

  takeWhile((v) => v < 4),

);

console.log(await Array.fromAsync(iter)); // [1, 2, 3]

```



### toAsyncIterable



Converts an iterable to an async iterable.



```ts

import { toAsyncIterable } from "@core/iterutil/async/to-async-iterable";



const iter = toAsyncIterable([1, 2, 3]);

console.log(await Array.fromAsync(iter)); // [1, 2, 3]

```



### uniq



Returns an iterable that yields the unique elements of the input iterable.



```ts

import { uniq } from "@core/iterutil/uniq";



const iter1 = uniq([1, 2, 2, 3, 3, 3]);

console.log(Array.from(iter1)); // [1, 2, 3]



const iter2 = uniq(

  [1, 2, 3, 4, 5, 6, 7, 8, 9],

  (v) => v % 4,

);

console.log(Array.from(iter2)); // [1, 2, 3, 4]

```



```ts

import { uniq } from "@core/iterutil/async/uniq";



const iter1 = uniq([1, 2, 2, 3, 3, 3]);

console.log(await Array.fromAsync(iter1)); // [1, 2, 3]



const iter2 = uniq(

  [1, 2, 3, 4, 5, 6, 7, 8, 9],

  (v) => v % 4,

);

console.log(await Array.fromAsync(iter2)); // [1, 2, 3, 4]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { uniq } from "@core/iterutil/pipe/uniq";



const iter1 = pipe(

  [1, 2, 2, 3, 3, 3],

  uniq(),

);

console.log(Array.from(iter1)); // [1, 2, 3]



const iter2 = pipe(

  [1, 2, 3, 4, 5, 6, 7, 8, 9],

  uniq((v) => v % 4),

);

console.log(Array.from(iter2)); // [1, 2, 3, 4]

```



```ts

import { pipe } from "@core/pipe";

import { uniq } from "@core/iterutil/pipe/async/uniq";



const iter1 = pipe(

  [1, 2, 2, 3, 3, 3],

  uniq(),

);

console.log(await Array.fromAsync(iter1)); // [1, 2, 3]



const iter2 = pipe(

  [1, 2, 3, 4, 5, 6, 7, 8, 9],

  uniq((v) => v % 4),

);

console.log(await Array.fromAsync(iter2)); // [1, 2, 3, 4]

```



### zip



Zips multiple iterables into a single iterable.



```ts

import { zip } from "@core/iterutil/zip";



const iter = zip([1, 2, 3], ["a", "b", "c"]);

console.log(Array.from(iter)); // [[1, "a"], [2, "b"], [3, "c"]]

```



```ts

import { zip } from "@core/iterutil/async/zip";



const iter = zip([1, 2, 3], ["a", "b", "c"]);

console.log(await Array.fromAsync(iter)); // [[1, "a"], [2, "b"], [3, "c"]]

```



Use `pipe` and `pipe/async` modules for [@core/pipe] package like.



```ts

import { pipe } from "@core/pipe";

import { zip } from "@core/iterutil/pipe/zip";



const iter = pipe(

  [1, 2, 3],

  zip(["a", "b", "c"]),

);

console.log(Array.from(iter)); // [[1, "a"], [2, "b"], [3, "c"]]

```



```ts

import { pipe } from "@core/pipe";

import { zip } from "@core/iterutil/pipe/async/zip";



const iter = pipe(

  [1, 2, 3],

  zip(["a", "b", "c"]),

);

console.log(await Array.fromAsync(iter)); // [[1, "a"], [2, "b"], [3, "c"]]

```



## License



The code follows MIT license written in [LICENSE](./LICENSE). Contributors need

to agree that any modifications sent in this repository follow the license.