Iterables Reference

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🔁 Iterable and AsyncIterable utils.

Usage

By default, all utils are meant to be used with Iterable values, to use AsyncIterable values the functions have to be imported from @lou.codes/iterables/asynchronous.

📦 Node

Install @lou.codes/iterables as a dependency:

1
pnpm add @lou.codes/iterables
2
# or
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npm install @lou.codes/iterables
4
# or
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yarn add @lou.codes/iterables

Import it and use it:

1
import { iterableToArray, map } from "@lou.codes/iterables";
2

3
const mapDouble = map((value: number) => value * 2);
4

5
iterableToArray(mapDouble([1, 2, 3])); // [2, 4, 6]

🦕 Deno

Import @lou.codes/iterables using the npm: prefix, and use it directly:

1
import { iterableToArray, map } from "npm:@lou.codes/iterables";
2

3
const mapDouble = map((value: number) => value * 2);
4

5
iterableToArray(mapDouble([1, 2, 3])); // [2, 4, 6]

🌎 Browser

Import @lou.codes/iterables using esm.sh, and use it directly:

1
<script type="module">
2
	import { iterableToArray, map } from "https://esm.sh/@lou.codes/iterables";
3

4
	const mapDouble = map(value => value * 2);
5

6
	iterableToArray(mapDouble([1, 2, 3])); // [2, 4, 6]
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</script>

Useful links

📝 Documentation: TypeDoc generated documentation.
⏳ Changelog: List of changes between versions.
✅ Tests Coverage: Coveralls page with tests coverage.

Module: Asynchronous

Asynchronous utils (Default import).

Asynchronous Common

createIterableIterator

▸ createIterableIterator<GeneratorFunction>(generatorFunction): GeneratorFunction extends () => IsomorphicIterator<Item> ? Readonly<GeneratorFunction<GeneratorFunction> extends (…_arguments: _Arguments) => AsyncIterator<Item, any, undefined> ? AsyncIterableIterator<Item> : IterableIterator<Item>> : never

Takes a generator function and returns an iterable iterator or asynchronous iterable iterator object.

Type parameters

Name	Type
`GeneratorFunction`	extends () => `IsomorphicIterator`

Parameters

Name	Type	Description
`generatorFunction`	`GeneratorFunction`	Generator to be used every time `[Symbol.iterator]` is called.

Returns

GeneratorFunction extends () => IsomorphicIterator<Item> ? Readonly<GeneratorFunction<GeneratorFunction> extends (…_arguments: _Arguments) => AsyncIterator<Item, any, undefined> ? AsyncIterableIterator<Item> : IterableIterator<Item>> : never

Iterable iterator object.

Example

1
const identityGenerator = function* (value) {
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	yield value;
3
};
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const iterableIterator = createIterableIterator(identityGenerator);
5

6
const fooIdentity = iterableIterator("foo");
7

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for (const value of fooIdentity) {
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	console.log(value); // "foo"
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}
11

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// Same IterableIterator as above, return values again:
13

14
for (const value of fooIdentity) {
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	console.log(value); // "foo"
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}

forEach

▸ forEach<Item>(callback): (iterable: IsomorphicIterable<Item>) => Promise<void>

For each function for iterables and asynchronous iterables.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`callback`	`Unary`<`Item`, `Awaitable`<`void`>>	Function to be called for every item of the iterable.

Returns

fn

Curried function that expects an iterable to loop over and has callback set in context.

▸ (iterable): Promise<void>

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Promise<void>

Example

1
const logEach = forEach(console.log);
2

3
logEach([1, 2, 3]); // Logs 1, 2 and 3 separately

Asynchronous Generators

append

▸ append<TailItem>(tailIterable): <InitialItem>(initialIterable: IsomorphicIterable<InitialItem>) => Readonly<AsyncIterableIterator<Awaited<InitialItem> | Awaited<TailItem>>>

Appends one iterable or asynchronous iterable to another.

Type parameters

Name
`TailItem`

Parameters

Name	Type	Description
`tailIterable`	`IsomorphicIterable`<`TailItem`>	Iterable or asynchronous to be appended.

Returns

fn

Curried generator function with tailIterable set in context.

▸ <InitialItem>(initialIterable): Readonly<AsyncIterableIterator<Awaited<InitialItem> | Awaited<TailItem>>>

Type parameters

Name
`InitialItem`

Parameters

Name	Type
`initialIterable`	`IsomorphicIterable`<`InitialItem`>

Returns

Readonly<AsyncIterableIterator<Awaited<InitialItem> | Awaited<TailItem>>>

Example

1
const appendNumbers = append([0, 1, 2, 3, 4]);
2

3
appendNumbers(["foo", "bar"]); // ["foo", "bar", 0, 1, 2, 3, 4]
4
appendNumbers([]); // [0, 1, 2, 3, 4]

drop

▸ drop(amount): <Item>(iterable: IsomorphicIterable<Item>) => Readonly<AsyncIterableIterator<Awaited<Item>>>

Drop the specified amount of items from the given iterable or asynchronous iterable.

Parameters

Name	Type	Description
`amount`	`number` \| `bigint`	Amount of items to drop.

Returns

fn

Curried function with amount in context.

▸ <Item>(iterable): Readonly<AsyncIterableIterator<Awaited<Item>>>

Type parameters

Name
`Item`

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Readonly<AsyncIterableIterator<Awaited<Item>>>

Example

1
const drop2 = drop(2);
2
drop2([1, 2, 3, 4, 5]); // [3, 4, 5]

filter

▸ filter<Item, Filtered>(predicate): (iterable: IsomorphicIterable<Item>) => Readonly<AsyncIterableIterator<Awaited<Filtered>>>

Filters items in an iterable or asynchronous iterable against a predicate and returns items that evaluated to true.

Type parameters

Name	Type
`Item`	`Item`
`Filtered`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Filtered`> extends `Single`<`never`> ? `Unary`<`Item`, `boolean`> : `Predicate`<`Item`, `Filtered`>	Predicate function to evaluate each item.

Returns

fn

Curried function with predicate set in context.

▸ (iterable): Readonly<AsyncIterableIterator<Awaited<Filtered>>>

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Readonly<AsyncIterableIterator<Awaited<Filtered>>>

Example

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const filterEven = filter((number: number) => number % 2 === 0);
2

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iterableToArray(filterEven([1, 2, 3, 4])); // [2, 4]
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iterableToArray(filterEven([1, 3, 5, 7])); // []

flat

▸ flat<Iterable>(iterable): Iterable extends IsomorphicIterable<Item> ? Readonly<Item extends IsomorphicIterable<SubItem> ? AsyncIterableIterator<SubItem> : AsyncIterableIterator<Item>> : never

Flattens one level of the given iterable or asynchronous iterable.

Type parameters

Name	Type
`Iterable`	extends `IsomorphicIterable`

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable to flatten.

Returns

Iterable extends IsomorphicIterable<Item> ? Readonly<Item extends IsomorphicIterable<SubItem> ? AsyncIterableIterator<SubItem> : AsyncIterableIterator<Item>> : never

Iterable with flatten items.

Example

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flat([1, 2, [3, 4]]); // [1, 2, 3, 4]

initial

▸ initial<Iterable>(iterable): IsomorphicIterableIterator<IsomorphicIterableItem<Iterable>>

Get all elements except the last one of an iterable or asynchronous iterable.

Type parameters

Name	Type
`Iterable`	extends `IsomorphicIterable`

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable to get the items from.

Returns

IsomorphicIterableIterator<IsomorphicIterableItem<Iterable>>

Iterable with all items except the last one.

Example

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initial([1, 2, 3]); // [1, 2]

intersperse

▸ intersperse<Separator>(separator): <Item>(iterable: IsomorphicIterable<Item>) => IsomorphicIterableIterator<Item | Awaited<Separator> | Awaited<Item>>

Add the given separator between each element of the given iterable or asynchronous iterable.

Type parameters

Name
`Separator`

Parameters

Name	Type	Description
`separator`	`Separator`	Separator to add between each element.

Returns

fn

Curried function with separator in context.

▸ <Item>(iterable): IsomorphicIterableIterator<Item | Awaited<Separator> | Awaited<Item>>

Type parameters

Name
`Item`

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

IsomorphicIterableIterator<Item | Awaited<Separator> | Awaited<Item>>

Example

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const intersperseComma = intersperse(",");
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intersperseComma([1, 2, 3]); // [1, ",", 2, ",", 3]

map

▸ map<Item, MappedItem>(mapper): (iterable: IsomorphicIterable<Item>) => Readonly<AsyncIterableIterator<Awaited<MappedItem>>>

Map for iterables and asynchronous iterables.

Type parameters

Name
`Item`
`MappedItem`

Parameters

Name	Type	Description
`mapper`	`Unary`<`Item`, `MappedItem`>	Mapper function.

Returns

fn

Generator function with mapper function set in context.

▸ (iterable): Readonly<AsyncIterableIterator<Awaited<MappedItem>>>

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Readonly<AsyncIterableIterator<Awaited<MappedItem>>>

Example

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const double = value => value * 2;
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const mapDouble = map(double);
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mapDouble([1, 2, 3]); // [2, 4, 6]

objectToEntries

▸ objectToEntries<Key, Value>(input): Readonly<AsyncIterableIterator<Entry<Key, Value>>>

Yields all entries of an object (including symbols).

Type parameters

Name	Type
`Key`	extends `PropertyKey`
`Value`	`Value`

Parameters

Name	Type	Description
`input`	`Readonly`<`Record`<`Key`, `Value`>>	Object to get entries from.

Returns

Readonly<AsyncIterableIterator<Entry<Key, Value>>>

Iterable with entries of the given object (including symbols).

Example

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const entries = objectEntries({ a: 1, b: 2 });
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entries.next(); // { value: ["a", 1], done: false }
3
entries.next(); // { value: ["b", 2], done: false }
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entries.next(); // { value: undefined, done: true }

prepend

▸ prepend<InitialItem>(initialIterable): <TailItem>(tailIterable: IsomorphicIterable<TailItem>) => Readonly<AsyncIterableIterator<Awaited<InitialItem> | Awaited<TailItem>>>

Prepends one iterable or asynchronous iterable to another.

Type parameters

Name
`InitialItem`

Parameters

Name	Type	Description
`initialIterable`	`IsomorphicIterable`<`InitialItem`>	Iterable or asynchronous iterable to be appended.

Returns

fn

Curried generator function with initialIterable set in context.

▸ <TailItem>(tailIterable): Readonly<AsyncIterableIterator<Awaited<InitialItem> | Awaited<TailItem>>>

Type parameters

Name
`TailItem`

Parameters

Name	Type
`tailIterable`	`IsomorphicIterable`<`TailItem`>

Returns

Readonly<AsyncIterableIterator<Awaited<InitialItem> | Awaited<TailItem>>>

Example

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const prependNumbers = prepend([0, 1, 2, 3, 4]);
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prependNumbers(["foo", "bar"]); // [0, 1, 2, 3, 4, "foo", "bar"]

random

▸ random(seed): (from: number) => (to: number) => Readonly<AsyncIterableIterator<number>>

Deterministic pseudo-random number generator.

⚠️ IMPORTANT: This only works in secure contexts (HTTPS/Node).

Parameters

Name	Type	Description
`seed`	`string` \| `Numeric`	Seed to be used to generate random numbers.

Returns

fn

Curried generator function with seed set in context.

▸ (from): (to: number) => Readonly<AsyncIterableIterator<number>>

Parameters

Name	Type
`from`	`number`

Returns

fn

▸ (to): Readonly<AsyncIterableIterator<number>>

Parameters

Name	Type
`to`	`number`

Returns

Readonly<AsyncIterableIterator<number>>

Example

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const seededRandom = random("some seed");
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const random0To10 = seededRandom(0)(10);
3

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[...pick(2)(random0To10)]; // Two "random" values between 0 and 10
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[...pick(2)(random0To10)]; // Same two "random" values between 0 and 10

See

range

▸ range<Step>(step): (from: Step extends bigint ? bigint : number) => (to: Step extends bigint ? bigint : number) => Readonly<AsyncIterableIterator<number | Step extends bigint ? bigint : number>>

Range iterable generator (from from to to).

Type parameters

Name	Type
`Step`	extends `number` \| `bigint`

Parameters

Name	Type	Description
`step`	`Step`	Step size.

Returns

fn

Curried function with step set in context.

▸ (from): (to: Step extends bigint ? bigint : number) => Readonly<AsyncIterableIterator<number | Step extends bigint ? bigint : number>>

Parameters

Name	Type
`from`	`Step` extends `bigint` ? `bigint` : `number`

Returns

fn

▸ (to): Readonly<AsyncIterableIterator<number | Step extends bigint ? bigint : number>>

Parameters

Name	Type
`to`	`Step` extends `bigint` ? `bigint` : `number`

Returns

Readonly<AsyncIterableIterator<number | Step extends bigint ? bigint : number>>

Example

1
[...range(1)(0)(5)]; // [0, 1, 2, 3, 4, 5]
2
[...range(1)(5)(0)]; // [5, 4, 3, 2, 1, 0]

repeat

▸ repeat(times): <Item>(item: Item) => Readonly<AsyncIterableIterator<Awaited<Item>>>

Repeat given item the specified amount of times (can be BigInt or Infinity times) as an iterable.

Parameters

Name	Type
`times`	`number` \| `bigint`

Returns

fn

Curried function with item in context.

▸ <Item>(item): Readonly<AsyncIterableIterator<Awaited<Item>>>

Type parameters

Name
`Item`

Parameters

Name	Type
`item`	`Item`

Returns

Readonly<AsyncIterableIterator<Awaited<Item>>>

Example

1
const repeat3Times = repeat(3);
2
repeat3Times("foo"); // ["foo", "foo", "foo"]

take

▸ take(amount): <Item>(iterable: IsomorphicIterable<Item>) => Readonly<AsyncIterableIterator<Awaited<Item>>>

Take the given amount of items from the iterable or asynchronous iterable.

Parameters

Name	Type	Description
`amount`	`number` \| `bigint`	Amount of items to take.

Returns

fn

Curried function with amount in context.

▸ <Item>(iterable): Readonly<AsyncIterableIterator<Awaited<Item>>>

Type parameters

Name
`Item`

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Readonly<AsyncIterableIterator<Awaited<Item>>>

Example

1
const take2 = take(2);
2
take2([1, 2, 3, 4, 5]); // [1, 2]

toIterable

▸ toIterable<ValueOrAsyncIterable>(valueOrIterable): Readonly<AsyncIterableIterator<ValueOrAsyncIterable extends IsomorphicIterable ? IsomorphicIterableItem<ValueOrAsyncIterable<ValueOrAsyncIterable>> : ValueOrAsyncIterable>>

Takes a value, iterable or asynchronous iterable and yields it.

Type parameters

Name
`ValueOrAsyncIterable`

Parameters

Name	Type	Description
`valueOrIterable`	`ValueOrAsyncIterable`	Vale or iterable to yield.

Returns

Readonly<AsyncIterableIterator<ValueOrAsyncIterable extends IsomorphicIterable ? IsomorphicIterableItem<ValueOrAsyncIterable<ValueOrAsyncIterable>> : ValueOrAsyncIterable>>

Yielded item or iterable.

Example

1
const iterable = toIterable(1);
2
const iterator = getIterator(iterable);
3
iterator.next(); // { value: 1, done: false }
4
iterator.next(); // { value: undefined, done: true }

See

createIterableIterator

unique

▸ unique<Item>(iterable): Readonly<AsyncIterableIterator<Awaited<Item>>>

Returns a single instance of each item in the iterable or asynchronous iterable.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`iterable`	`IsomorphicIterable`<`Item`>	Iterable to be filtered.

Returns

Readonly<AsyncIterableIterator<Awaited<Item>>>

Generators with a single instance of each item of the iterable.

Example

1
unique([1, 2, 3, 4, 1, 2, 3, 4]); // [1, 2, 3, 4]

zip

▸ zip<ItemFirst>(iterableFirst): <ItemSecond>(iterableSecond: IsomorphicIterable<ItemSecond>) => Readonly<AsyncIterableIterator<readonly [ItemFirst | Awaited<ItemFirst>, ItemSecond]>>

Takes two iterables or asynchronous iterable and returns a new iterable or asynchronous iterable with the length of the shortest iterable with tuples containing the items from both.

Type parameters

Name
`ItemFirst`

Parameters

Name	Type	Description
`iterableFirst`	`IsomorphicIterable`<`ItemFirst`>	One of the iterables to be zipped.

Returns

fn

Curried function with iterableFirst in context.

▸ <ItemSecond>(iterableSecond): Readonly<AsyncIterableIterator<readonly [ItemFirst | Awaited<ItemFirst>, ItemSecond]>>

Type parameters

Name
`ItemSecond`

Parameters

Name	Type
`iterableSecond`	`IsomorphicIterable`<`ItemSecond`>

Returns

Readonly<AsyncIterableIterator<readonly [ItemFirst | Awaited<ItemFirst>, ItemSecond]>>

Example

1
const zipNumbers = zip([0, 1, 2]);
2
zipNumbers([3, 4, 5]); // [[0, 3], [1, 4], [2, 5]]

zipIndex

▸ zipIndex<ItemSecond>(iterableSecond): Readonly<AsyncIterableIterator<readonly [number, ItemSecond]>>

Yields a tuple for each item in the iterable with the index of said item.

Type parameters

Name
`ItemSecond`

Parameters

Name	Type
`iterableSecond`	`IsomorphicIterable`<`ItemSecond`>

Returns

Readonly<AsyncIterableIterator<readonly [number, ItemSecond]>>

Example

1
zipIndex(["foo", "bar"]); // [[0, "foo"], [1, "bar"]]

Yields

Tuples with the index of each item.

Asynchronous Reducers

count

▸ count<Item>(predicate): (iterable: IsomorphicIterable<Item>) => Promise<number>

Counts the number of items that satisfy a predicate in the given iterable or asynchronous iterable.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`predicate`	`Filter`<`Item`>	Predicate function for items to be counted.

Returns

fn

Curried function with predicate in context.

▸ (iterable): Promise<number>

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Promise<number>

Example

1
const countOdds = count((number: number) => number % 2 !== 1);
2
countOdds([1, 2, 3, 4, 5]); // 3
3
countOdds([0, 2, 4, 6, 8]); // 0

entriesToObject

▸ entriesToObject<Item>(iterable): Promise<Readonly<Record<EntryKey<Item>, EntryValue<Item>>>>

Takes an entries iterable or asynchronous iterable and returns an object.

Type parameters

Name	Type
`Item`	extends `Entry`

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Promise<Readonly<Record<EntryKey<Item>, EntryValue<Item>>>>

Object constructed from entries.

Example

1
entriesToObject([["key", "value"]]); // { key: "value" }
2
entriesToObject([
3
	["foo", "bar"],
4
	["number", 1],
5
]); // { foo: "bar", number: 1 }

every

▸ every<Item, Predicated>(predicate): (iterable: IsomorphicIterable<Item>) => Promise<boolean>

Evaluates items in an iterable or asynchronous iterable against a predicate and returns true if all items evaluates to true.

Type parameters

Name	Type
`Item`	`Item`
`Predicated`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Predicated`> extends `Single`<`never`> ? `Unary`<`Item`, `boolean`> : `Predicate`<`Item`, `Predicated`>	Predicate function to evaluate each item.

Returns

fn

Curried function with predicate set in context.

▸ (iterable): Promise<boolean>

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Promise<boolean>

Example

1
const everyEven = every((number: number) => number % 2 === 0);
2
everyEven([2, 4, 6, 8]); // true
3
everyEven([1, 2, 3, 4]); // false

find

▸ find<Item>(predicate): (iterable: IsomorphicIterable<Item>) => Promise<Maybe<Item>>

Returns the value of the first item in the iterable or asynchronous iterable where predicate is true, undefined otherwise.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`predicate`	`Unary`<`Item`, `boolean`>	Predicate function to search for item.

Returns

fn

Curried function with predicate set in context.

▸ (iterable): Promise<Maybe<Item>>

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Promise<Maybe<Item>>

Example

1
const findEven = find((number: number) => number % 2 === 0);
2
findEven([1, 2, 3, 4]); // 2
3
findEven([1, 3, 5, 7]); // undefined

groupBy

▸ groupBy<Item, Key>(grouper): <Iterable>(iterable: Iterable) => Iterable extends AsyncIterable<unknown> ? Promise<Readonly<Record<Key, ReadOnlyArray<Item>>>> : Readonly<Record<Key, ReadOnlyArray<Item>>>

Groups values of an iterable or asynchronous iterable in an object based on the output of the grouper function.

Type parameters

Name	Type
`Item`	`Item`
`Key`	extends `PropertyKey`

Parameters

Name	Type	Description
`grouper`	`Unary`<`Item`, `Key`>	Grouper function.

Returns

fn

Object with grouped values.

▸ <Iterable>(iterable): Iterable extends AsyncIterable<unknown> ? Promise<Readonly<Record<Key, ReadOnlyArray<Item>>>> : Readonly<Record<Key, ReadOnlyArray<Item>>>

Type parameters

Name	Type
`Iterable`	extends `IsomorphicIterable`<`Item`>

Parameters

Name	Type
`iterable`	`Iterable`

Returns

Iterable extends AsyncIterable<unknown> ? Promise<Readonly<Record<Key, ReadOnlyArray<Item>>>> : Readonly<Record<Key, ReadOnlyArray<Item>>>

Example

1
const groupByType = groupBy((value: number) =>
2
	number % 2 === 0 ? "even" : "odd",
3
);
4
groupByType([1, 2, 3, 4, 5]); // { even: [2, 4], odd: [1, 3, 5] }

head

▸ head<Iterable>(iterable): Iterable extends ReadOnlyArray ? Head<Iterable<Iterable>> : Maybe<IsomorphicIterableItem<Iterable>>

Get first element of an iterable or asynchronous iterable (undefined if it is empty).

Type parameters

Name	Type
`Iterable`	extends `IsomorphicIterable`

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable to get the first element from.

Returns

Iterable extends ReadOnlyArray ? Head<Iterable<Iterable>> : Maybe<IsomorphicIterableItem<Iterable>>

First element of the iterable (undefined if empty).

Example

1
head([1, 2, 3]); // 1

includes

▸ includes<SearchItem>(searchItem): (iterable: IsomorphicIterable<unknown>) => Promise<boolean>

Tries to find the given searchItem in iterable or asynchronous iterable.

Type parameters

Name
`SearchItem`

Parameters

Name	Type	Description
`searchItem`	`SearchItem`	Item to search.

Returns

fn

Curried function with searchItem set in context.

▸ (iterable): Promise<boolean>

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`unknown`>

Returns

Promise<boolean>

Example

1
const includesTwo = includes(2);
2
includesTwo([1, 2, 3, 4]); // true
3
includesTwo([1, 3, 5, 7]); // false

iterableToArray

▸ iterableToArray<Iterable>(iterable): Promise<ReadOnlyArray<IsomorphicIterableItem<Iterable>>>

Turns given iterable or asynchronous iterable into an array.

Type parameters

Name	Type
`Iterable`	extends `IsomorphicIterable`

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable to be turned into an array.

Returns

Promise<ReadOnlyArray<IsomorphicIterableItem<Iterable>>>

Array made of iterable items.

Example

1
iterableToArray([1, 2, 3, 4]); // [1, 2, 3, 4]

join

▸ join(separator): <Iterable>(iterable: Iterable) => Iterable extends AsyncIterable<unknown> ? Promise<string> : string

Takes a separator string and a iterable or asynchronous iterable and returns a string with the concatenation of all the elements separated by the separator.

Parameters

Name	Type	Description
`separator`	`string`	String to use as separator.

Returns

fn

Curried function with separator in context.

▸ <Iterable>(iterable): Iterable extends AsyncIterable<unknown> ? Promise<string> : string

Type parameters

Name	Type
`Iterable`	extends `IsomorphicIterable`

Parameters

Name	Type
`iterable`	`Iterable`

Returns

Iterable extends AsyncIterable<unknown> ? Promise<string> : string

Example

1
const joinWithSpaces = join(" ");
2
joinWithSpaces([1, 2, 3]); // "1 2 3"

length

▸ length<Iterable>(iterable): Iterable extends AsyncIterable<unknown> ? Promise<number> : number

Get the length of an iterable or asynchronous iterable.

Type parameters

Name	Type
`Iterable`	extends `IsomorphicIterable`<`unknown`>

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable or asynchronous iterable to get the length from.

Returns

Iterable extends AsyncIterable<unknown> ? Promise<number> : number

Promise with the length of the iterable.

Example

1
length([1, 2, 3]); // 3

reduce

▸ reduce<Item, Accumulator>(reducer): (initialValue: Accumulator) => <Iterable>(iterable: Iterable) => Iterable extends AsyncIterable<unknown> ? Promise<Accumulator> : Accumulator

Reducer function for iterables and asynchronous iterables.

Type parameters

Name
`Item`
`Accumulator`

Parameters

Name	Type	Description
`reducer`	`Unary`<`Item`, `Unary`<`Accumulator`, `Awaitable`<`Accumulator`>>>	Reducer function.

Returns

fn

Curried function with reducer in context.

▸ (initialValue): <Iterable>(iterable: Iterable) => Iterable extends AsyncIterable<unknown> ? Promise<Accumulator> : Accumulator

Parameters

Name	Type
`initialValue`	`Accumulator`

Returns

fn

▸ <Iterable>(iterable): Iterable extends AsyncIterable<unknown> ? Promise<Accumulator> : Accumulator

Type parameters

Name	Type
`Iterable`	extends `IsomorphicIterable`<`Item`>

Parameters

Name	Type
`iterable`	`Iterable`

Returns

Iterable extends AsyncIterable<unknown> ? Promise<Accumulator> : Accumulator

Example

1
const sum = Accumulator<number>(item => total => total + item);
2
const sumFrom0 = sum(0);
3

4
sumFrom0([1, 2, 3]); // 6

some

▸ some<Item, Predicated>(predicate): (iterable: IsomorphicIterable<Item>) => Promise<boolean>

Evaluates items in an iterable or asynchronous iterable against a predicate and returns true if any item evaluates to true.

Type parameters

Name	Type
`Item`	`Item`
`Predicated`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Predicated`> extends `Single`<`never`> ? `Unary`<`Item`, `boolean`> : `Predicate`<`Item`, `Predicated`>	Predicate function to evaluate each item.

Returns

fn

Curried function with predicate set in context.

▸ (iterable): Promise<boolean>

Parameters

Name	Type
`iterable`	`IsomorphicIterable`<`Item`>

Returns

Promise<boolean>

Example

1
const someEven = some((number: number) => number % 2 === 0);
2
someEven([1, 2, 3, 4]); // true
3
someEven([1, 3, 5, 7]); // false

Module: Synchronous

Synchronous utils (Default import).

Common

createIterableIterator

▸ createIterableIterator<Item>(generatorFunction): Readonly<IterableIterator<Item>>

Takes a generator function and returns an iterable iterator object.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`generatorFunction`	() => `Readonly`<`Iterator`<`Item`, `void`, `void`>>	Generator to be used every time `[Symbol.iterator]` is called.

Returns

Readonly<IterableIterator<Item>>

Iterable iterator object.

Example

1
const identityGenerator = function* (value) {
2
	yield value;
3
};
4
const iterableIterator = createIterableIterator(identityGenerator);
5

6
const fooIdentity = iterableIterator("foo");
7

8
for (const value of fooIdentity) {
9
	console.log(value); // "foo"
10
}
11

12
// Same IterableIterator as above, return values again:
13

14
for (const value of fooIdentity) {
15
	console.log(value); // "foo"
16
}

forEach

▸ forEach<Item>(callback): (iterable: Readonly<Iterable<Item>>) => void

For each function for iterables.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`callback`	`Unary`<`Item`, `void`>	Function to be called for every item of the iterable.

Returns

fn

Curried function that expects an iterable to loop over and has callback set in context.

▸ (iterable): void

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

void

Example

1
const logEach = forEach(console.log);
2

3
logEach([1, 2, 3]); // Logs 1, 2 and 3 separately

Generators

append

▸ append<TailItem>(tailIterable): <InitialItem>(initialIterable: Readonly<Iterable<InitialItem>>) => Readonly<IterableIterator<TailItem | InitialItem>>

Appends one iterable to another.

Type parameters

Name
`TailItem`

Parameters

Name	Type	Description
`tailIterable`	`Readonly`<`Iterable`<`TailItem`>>	Iterable to be appended.

Returns

fn

Curried generator function with tailIterable set in context.

▸ <InitialItem>(initialIterable): Readonly<IterableIterator<TailItem | InitialItem>>

Type parameters

Name
`InitialItem`

Parameters

Name	Type
`initialIterable`	`Readonly`<`Iterable`<`InitialItem`>>

Returns

Readonly<IterableIterator<TailItem | InitialItem>>

Example

1
const appendNumbers = append([0, 1, 2, 3, 4]);
2

3
appendNumbers(["foo", "bar"]); // ["foo", "bar", 0, 1, 2, 3, 4]
4
appendNumbers([]); // [0, 1, 2, 3, 4]

drop

▸ drop(amount): <Item>(iterable: Readonly<Iterable<Item>>) => Readonly<IterableIterator<Item>>

Drop the specified amount of items from the given iterable.

Parameters

Name	Type	Description
`amount`	`number` \| `bigint`	Amount of items to drop.

Returns

fn

Curried function with amount in context.

▸ <Item>(iterable): Readonly<IterableIterator<Item>>

Type parameters

Name
`Item`

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Readonly<IterableIterator<Item>>

Example

1
const drop2 = drop(2);
2
drop2([1, 2, 3, 4, 5]); // [3, 4, 5]

filter

▸ filter<Item, Filtered>(predicate): (iterable: Readonly<Iterable<Item>>) => Readonly<IterableIterator<Filtered>>

Filters items in an iterable against a predicate and returns items that evaluated to true.

Type parameters

Name	Type
`Item`	`Item`
`Filtered`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Filtered`> extends `Single`<`never`> ? `Unary`<`Item`, `boolean`> : `Predicate`<`Item`, `Filtered`>	Predicate function to evaluate each item.

Returns

fn

Curried function with predicate set in context.

▸ (iterable): Readonly<IterableIterator<Filtered>>

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Readonly<IterableIterator<Filtered>>

Example

1
const filterEven = filter((number: number) => number % 2 === 0);
2

3
iterableToArray(filterEven([1, 2, 3, 4])); // [2, 4]
4
iterableToArray(filterEven([1, 3, 5, 7])); // []

flat

▸ flat<Iterable>(iterable): Iterable extends Readonly<Iterable<Item>> ? Item extends Readonly<Iterable<SubItem>> ? Readonly<IterableIterator<SubItem>> : Readonly<IterableIterator<Item>> : never

Flattens one level of the given iterable.

Type parameters

Name	Type
`Iterable`	extends `Readonly`<`Iterable`<`unknown`>>

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable to flatten.

Returns

Iterable extends Readonly<Iterable<Item>> ? Item extends Readonly<Iterable<SubItem>> ? Readonly<IterableIterator<SubItem>> : Readonly<IterableIterator<Item>> : never

Iterable with flatten items.

Example

1
flat([1, 2, [3, 4]]); // [1, 2, 3, 4]

initial

▸ initial<Iterable>(iterable): Readonly<IterableIterator<Iterable extends ReadOnlyArray ? Initial<Iterable<Iterable>>[number] : IsomorphicIterableItem<Iterable>>>

Get all elements except the last one of an iterable.

Type parameters

Name	Type
`Iterable`	extends `Readonly`<`Iterable`<`unknown`>>

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable to get the items from.

Returns

Readonly<IterableIterator<Iterable extends ReadOnlyArray ? Initial<Iterable<Iterable>>[number] : IsomorphicIterableItem<Iterable>>>

Iterable with all items except the last one.

Example

1
initial([1, 2, 3]); // [1, 2]

intersperse

▸ intersperse<Separator>(separator): <Item>(iterable: Readonly<Iterable<Item>>) => Readonly<IterableIterator<Separator | Item>>

Add the given separator between each element of the given iterable.

Type parameters

Name
`Separator`

Parameters

Name	Type	Description
`separator`	`Separator`	Separator to add between each element.

Returns

fn

Curried function with separator in context.

▸ <Item>(iterable): Readonly<IterableIterator<Separator | Item>>

Type parameters

Name
`Item`

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Readonly<IterableIterator<Separator | Item>>

Example

1
const intersperseComma = intersperse(",");
2
intersperseComma([1, 2, 3]); // [1, ",", 2, ",", 3]

map

▸ map<Item, MappedItem>(mapper): (iterable: Readonly<Iterable<Item>>) => Readonly<IterableIterator<MappedItem>>

Map for iterables.

Type parameters

Name
`Item`
`MappedItem`

Parameters

Name	Type	Description
`mapper`	`Unary`<`Item`, `MappedItem`>	Mapper function.

Returns

fn

Generator function with mapper function set in context.

▸ (iterable): Readonly<IterableIterator<MappedItem>>

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Readonly<IterableIterator<MappedItem>>

Example

1
const double = value => value * 2;
2
const mapDouble = map(double);
3

4
mapDouble([1, 2, 3]); // [2, 4, 6]

objectToEntries

▸ objectToEntries<Key, Value>(input): Readonly<IterableIterator<Entry<Key, Value>>>

Yields all entries of an object (including symbols).

Type parameters

Name	Type
`Key`	extends `PropertyKey`
`Value`	`Value`

Parameters

Name	Type	Description
`input`	`Readonly`<`Record`<`Key`, `Value`>>	Object to get entries from.

Returns

Readonly<IterableIterator<Entry<Key, Value>>>

Iterable with entries of the given object (including symbols).

Example

1
const entries = objectEntries({ a: 1, b: 2 });
2
entries.next(); // { value: ["a", 1], done: false }
3
entries.next(); // { value: ["b", 2], done: false }
4
entries.next(); // { value: undefined, done: true }

prepend

▸ prepend<InitialItem>(initialIterable): <TailItem>(tailIterable: Readonly<Iterable<TailItem>>) => Readonly<IterableIterator<InitialItem | TailItem>>

Prepends one iterable to another.

Type parameters

Name
`InitialItem`

Parameters

Name	Type	Description
`initialIterable`	`Readonly`<`Iterable`<`InitialItem`>>	Iterable to be appended.

Returns

fn

Curried generator function with initialIterable set in context.

▸ <TailItem>(tailIterable): Readonly<IterableIterator<InitialItem | TailItem>>

Type parameters

Name
`TailItem`

Parameters

Name	Type
`tailIterable`	`Readonly`<`Iterable`<`TailItem`>>

Returns

Readonly<IterableIterator<InitialItem | TailItem>>

Example

1
const prependNumbers = prepend([0, 1, 2, 3, 4]);
2
prependNumbers(["foo", "bar"]); // [0, 1, 2, 3, 4, "foo", "bar"]

range

▸ range<Step>(step): (from: Step extends bigint ? bigint : number) => (to: Step extends bigint ? bigint : number) => Readonly<IterableIterator<number | Step extends bigint ? bigint : number>>

Range iterable generator (from from to to).

Type parameters

Name	Type
`Step`	extends `number` \| `bigint`

Parameters

Name	Type	Description
`step`	`Step`	Step size.

Returns

fn

Curried function with step set in context.

▸ (from): (to: Step extends bigint ? bigint : number) => Readonly<IterableIterator<number | Step extends bigint ? bigint : number>>

Parameters

Name	Type
`from`	`Step` extends `bigint` ? `bigint` : `number`

Returns

fn

▸ (to): Readonly<IterableIterator<number | Step extends bigint ? bigint : number>>

Parameters

Name	Type
`to`	`Step` extends `bigint` ? `bigint` : `number`

Returns

Readonly<IterableIterator<number | Step extends bigint ? bigint : number>>

Example

1
[...range(1)(0)(5)]; // [0, 1, 2, 3, 4, 5]
2
[...range(1)(5)(0)]; // [5, 4, 3, 2, 1, 0]

repeat

▸ repeat(times): <Item>(item: Item) => Readonly<IterableIterator<Item>>

Repeat given item the specified amount of times (can be BigInt or Infinity times) as an iterable.

Parameters

Name	Type
`times`	`number` \| `bigint`

Returns

fn

Curried function with item in context.

▸ <Item>(item): Readonly<IterableIterator<Item>>

Type parameters

Name
`Item`

Parameters

Name	Type
`item`	`Item`

Returns

Readonly<IterableIterator<Item>>

Example

1
const repeat3Times = repeat(3);
2
repeat3Times("foo"); // ["foo", "foo", "foo"]

take

▸ take(amount): <Item>(iterable: Readonly<Iterable<Item>>) => Readonly<IterableIterator<Item>>

Take the given amount of items from the iterable.

Parameters

Name	Type	Description
`amount`	`number` \| `bigint`	Amount of items to take.

Returns

fn

Curried function with amount in context.

▸ <Item>(iterable): Readonly<IterableIterator<Item>>

Type parameters

Name
`Item`

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Readonly<IterableIterator<Item>>

Example

1
const take2 = take(2);
2
take2([1, 2, 3, 4, 5]); // [1, 2]

toIterable

▸ toIterable<ValueOrIterable>(valueOrIterable): Readonly<IterableIterator<ValueOrIterable extends IsomorphicIterable ? IsomorphicIterableItem<ValueOrIterable<ValueOrIterable>> : ValueOrIterable>>

Takes a value, iterable and yields it.

Type parameters

Name	Description
`ValueOrIterable`	Generic of value or iterable to yield.

Parameters

Name	Type	Description
`valueOrIterable`	`ValueOrIterable`	Vale or iterable to yield.

Returns

Readonly<IterableIterator<ValueOrIterable extends IsomorphicIterable ? IsomorphicIterableItem<ValueOrIterable<ValueOrIterable>> : ValueOrIterable>>

Yielded item or iterable.

Example

1
const iterable = toIterable(1);
2
const iterator = getIterator(iterable);
3
iterator.next(); // { value: 1, done: false }
4
iterator.next(); // { value: undefined, done: true }

See

createIterableIterator

unique

▸ unique<Item>(iterable): Readonly<IterableIterator<Item>>

Returns a single instance of each item in the iterable.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`iterable`	`Readonly`<`Iterable`<`Item`>>	Iterable to be filtered.

Returns

Readonly<IterableIterator<Item>>

Generators with a single instance of each item of the iterable.

Example

1
unique([1, 2, 3, 4, 1, 2, 3, 4]); // [1, 2, 3, 4]

zip

▸ zip<ItemFirst>(iterableFirst): <ItemSecond>(iterableSecond: Readonly<Iterable<ItemSecond>>) => Readonly<IterableIterator<readonly [ItemFirst, ItemSecond]>>

Takes two iterables and returns a new iterable with the length of the shortest iterable with tuples containing the items from both.

Type parameters

Name
`ItemFirst`

Parameters

Name	Type	Description
`iterableFirst`	`Readonly`<`Iterable`<`ItemFirst`>>	One of the iterables to be zipped.

Returns

fn

Curried function with iterableFirst in context.

▸ <ItemSecond>(iterableSecond): Readonly<IterableIterator<readonly [ItemFirst, ItemSecond]>>

Type parameters

Name
`ItemSecond`

Parameters

Name	Type
`iterableSecond`	`Readonly`<`Iterable`<`ItemSecond`>>

Returns

Readonly<IterableIterator<readonly [ItemFirst, ItemSecond]>>

Example

1
const zipNumbers = zip([0, 1, 2]);
2
zipNumbers([3, 4, 5]); // [[0, 3], [1, 4], [2, 5]]

zipIndex

▸ zipIndex<ItemSecond>(iterableSecond): Readonly<IterableIterator<readonly [number, ItemSecond]>>

Yields a tuple for each item in the iterable with the index of said item.

Type parameters

Name
`ItemSecond`

Parameters

Name	Type
`iterableSecond`	`Readonly`<`Iterable`<`ItemSecond`>>

Returns

Readonly<IterableIterator<readonly [number, ItemSecond]>>

Example

1
zipIndex(["foo", "bar"]); // [[0, "foo"], [1, "bar"]]

Yields

Tuples with the index of each item.

Reducers

count

▸ count<Item>(predicate): (iterable: Readonly<Iterable<Item>>) => number

Counts the number of items that satisfy a predicate in the given iterable.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`predicate`	`Filter`<`Item`>	Predicate function for items to be counted.

Returns

fn

Curried function with predicate in context.

▸ (iterable): number

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

number

Example

1
const countOdds = count((number: number) => number % 2 !== 1);
2
countOdds([1, 2, 3, 4, 5]); // 3
3
countOdds([0, 2, 4, 6, 8]); // 0

entriesToObject

▸ entriesToObject<Item>(iterable): Readonly<Record<EntryKey<Item>, EntryValue<Item>>>

Takes an entries iterable and returns an object.

Type parameters

Name	Type
`Item`	extends `Entry`

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Readonly<Record<EntryKey<Item>, EntryValue<Item>>>

Object constructed from entries.

Example

1
entriesToObject([["key", "value"]]); // { key: "value" }
2
entriesToObject([
3
	["foo", "bar"],
4
	["number", 1],
5
]); // { foo: "bar", number: 1 }

every

▸ every<Item, Predicated>(predicate): (iterable: Readonly<Iterable<Item>>) => boolean

Evaluates items in an iterable against a predicate and returns true if all items evaluates to true.

Type parameters

Name	Type
`Item`	`Item`
`Predicated`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Predicated`> extends `Single`<`never`> ? `Unary`<`Item`, `boolean`> : `Predicate`<`Item`, `Predicated`>	Predicate function to evaluate each item.

Returns

fn

Curried function with predicate set in context.

▸ (iterable): boolean

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

boolean

Example

1
const everyEven = every((number: number) => number % 2 === 0);
2
everyEven([2, 4, 6, 8]); // true
3
everyEven([1, 2, 3, 4]); // false

find

▸ find<Item>(predicate): (iterable: Readonly<Iterable<Item>>) => Maybe<Item>

Returns the value of the first item in the iterable where predicate is true, undefined otherwise.

Type parameters

Name
`Item`

Parameters

Name	Type	Description
`predicate`	`Unary`<`Item`, `boolean`>	Predicate function to search for item.

Returns

fn

Curried function with predicate set in context.

▸ (iterable): Maybe<Item>

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Maybe<Item>

Example

1
const findEven = find((number: number) => number % 2 === 0);
2
findEven([1, 2, 3, 4]); // 2
3
findEven([1, 3, 5, 7]); // undefined

groupBy

▸ groupBy<Item, Key>(grouper): (iterable: Readonly<Iterable<Item>>) => Readonly<Record<Key, ReadOnlyArray<Item>>>

Groups values of an iterable in an object based on the output of the grouper function.

Type parameters

Name	Type
`Item`	`Item`
`Key`	extends `PropertyKey`

Parameters

Name	Type	Description
`grouper`	`Unary`<`Item`, `Key`>	Grouper function.

Returns

fn

Object with grouped values.

▸ (iterable): Readonly<Record<Key, ReadOnlyArray<Item>>>

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Readonly<Record<Key, ReadOnlyArray<Item>>>

Example

1
const groupByType = groupBy((value: number) =>
2
	number % 2 === 0 ? "even" : "odd",
3
);
4
groupByType([1, 2, 3, 4, 5]); // { even: [2, 4], odd: [1, 3, 5] }

head

▸ head<Iterable>(iterable): Iterable extends ReadOnlyArray ? Head<Iterable<Iterable>> : Maybe<IsomorphicIterableItem<Iterable>>

Get first element of an iterable (undefined if it is empty).

Type parameters

Name	Type
`Iterable`	extends `Readonly`<`Iterable`<`unknown`>>

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable to get the first element from.

Returns

Iterable extends ReadOnlyArray ? Head<Iterable<Iterable>> : Maybe<IsomorphicIterableItem<Iterable>>

First element of the iterable (undefined if empty).

Example

1
head([1, 2, 3]); // 1

includes

▸ includes<SearchItem>(searchItem): (iterable: Readonly<Iterable<unknown>>) => boolean

Tries to find the given searchItem in iterable.

Type parameters

Name
`SearchItem`

Parameters

Name	Type	Description
`searchItem`	`SearchItem`	Item to search.

Returns

fn

Curried function with searchItem set in context.

▸ (iterable): boolean

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`unknown`>>

Returns

boolean

Example

1
const includesTwo = includes(2);
2
includesTwo([1, 2, 3, 4]); // true
3
includesTwo([1, 3, 5, 7]); // false

iterableToArray

▸ iterableToArray<Iterable>(iterable): ReadOnlyArray<IsomorphicIterableItem<Iterable>>

Turns given iterable into an array.

Type parameters

Name	Type
`Iterable`	extends `Readonly`<`Iterable`<`unknown`>>

Parameters

Name	Type	Description
`iterable`	`Iterable`	Iterable to be turned into an array.

Returns

ReadOnlyArray<IsomorphicIterableItem<Iterable>>

Array made of iterable items.

Example

1
iterableToArray([1, 2, 3, 4]); // [1, 2, 3, 4]

join

▸ join(separator): <Item>(iterable: Readonly<Iterable<Item>>) => string

Takes a separator string and a iterable and returns a string with the concatenation of all the elements separated by the separator.

Parameters

Name	Type	Description
`separator`	`string`	String to use as separator.

Returns

fn

Curried function with separator in context.

▸ <Item>(iterable): string

Type parameters

Name	Type
`Item`	extends `Strigifiable`

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

string

Example

1
const joinWithSpaces = join(" ");
2
joinWithSpaces([1, 2, 3]); // "1 2 3"

length

▸ length(iterable): number

Get the length of an iterable.

Parameters

Name	Type	Description
`iterable`	`Readonly`<`Iterable`<`unknown`>>	Iterable to get the length from.

Returns

number

Promise with the length of the iterable.

Example

1
length([1, 2, 3]); // 3

reduce

▸ reduce<Item, Accumulator>(reducer): (initialValue: Accumulator) => (iterable: Readonly<Iterable<Item>>) => Accumulator

Reducer function for iterables.

Type parameters

Name
`Item`
`Accumulator`

Parameters

Name	Type	Description
`reducer`	`Reducer`<`Item`, `Accumulator`>	Reducer function.

Returns

fn

Curried function with reducer in context.

▸ (initialValue): (iterable: Readonly<Iterable<Item>>) => Accumulator

Parameters

Name	Type
`initialValue`	`Accumulator`

Returns

fn

▸ (iterable): Accumulator

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

Accumulator

Example

1
const sum = reduce<number>(item => total => total + item);
2
const sumFrom0 = sum(0);
3

4
sumFrom0([1, 2, 3]); // 6

some

▸ some<Item, Predicated>(predicate): (iterable: Readonly<Iterable<Item>>) => boolean

Evaluates items in an iterable against a predicate and returns true if any item evaluates to true.

Type parameters

Name	Type
`Item`	`Item`
`Predicated`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Predicated`> extends `Single`<`never`> ? `Unary`<`Item`, `boolean`> : `Predicate`<`Item`, `Predicated`>	Predicate function to evaluate each item.

Returns

fn

Curried function with predicate set in context.

▸ (iterable): boolean

Parameters

Name	Type
`iterable`	`Readonly`<`Iterable`<`Item`>>

Returns

boolean

Example

1
const someEven = some((number: number) => number % 2 === 0);
2
someEven([1, 2, 3, 4]); // true
3
someEven([1, 3, 5, 7]); // false