Utils by Lou

Coverage License NPM Version Open Issues

⚒️ Lou’s TypeScript curried functional utils.

Usage

📦 Node

Install @lou.codes/utils as a dependency:

pnpm add @lou.codes/utils
# or
npm install @lou.codes/utils
# or
yarn add @lou.codes/utils

Import it and use it:

import { get } from "@lou.codes/utils";

get("foo")({ foo: "bar" }); // "bar"

🦕 Deno

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

import { get } from "npm:@lou.codes/utils";

get("foo")({ foo: "bar" }); // "bar"

🌎 Browser

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

<script type="module">
	import { get } from "https://esm.sh/@lou.codes/utils";

	get("foo")({ foo: "bar" }); // "bar"
</script>

Useful links

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

Classes

bind

▸ bind<Context>(context): <Method>(method: Method) => Method

Bounds the given context to the given method.

Type parameters

Name
`Context`

Parameters

Name	Type
`context`	`Context`

Returns

fn

Curried function with context in context.

▸ <Method>(method): Method

Type parameters

Name	Type
`Method`	extends `Function`

Parameters

Name	Type
`method`	`Method`

Returns

Method

Example

const bindConsole = bind(console);
const log = bindConsole(console.log);

log("Hello world!"); // Logs "Hello world!" without context errors.

construct

▸ construct<Constructor>(constructor): (…constructorArguments: ConstructorParameters<Constructor>) => InstanceType<Constructor>

Creates a new instance of the given constructor with the given arguments.

Type parameters

Name	Type
`Constructor`	extends `Class`<`never`>

Parameters

Name	Type
`constructor`	`Constructor`

Returns

fn

Curried function with constructor in context.

▸ (...constructorArguments): InstanceType<Constructor>

Parameters

Name	Type
`...constructorArguments`	`ConstructorParameters`<`Constructor`>

Returns

InstanceType<Constructor>

Example

const constructDate = construct(Date);

constructDate(); // Returns the current Date (like `new Date()`).

constructArray

▸ constructArray<Item>(length): Item[]

Functional alias for new Array().

Type parameters

Name
`Item`

Parameters

Name	Type
`length`	`number`

Returns

Item[]

▸ constructArray<Items>(...items): Items[number][]

Functional alias for new Array().

Type parameters

Name	Type
`Items`	extends `ReadOnlyArray`

Parameters

Name	Type
`...items`	`Items`

Returns

Items[number][]

constructDate

▸ constructDate(date?): Date

Functional alias for new Date().

Parameters

Name Type

date (optional) string | number | { getVarDate: () => VarDate ; [toPrimitive]: (hint: "default") => string(hint: "string") => string(hint: "number") => number(hint: string) => string | number ; getDate: () => number ; getDay: () => number ; getFullYear: () => number ; getHours: () => number ; getMilliseconds: () => number ; getMinutes: () => number ; getMonth: () => number ; getSeconds: () => number ; getTime: () => number ; getTimezoneOffset: () => number ; getUTCDate: () => number ; getUTCDay: () => number ; getUTCFullYear: () => number ; getUTCHours: () => number ; getUTCMilliseconds: () => number ; getUTCMinutes: () => number ; getUTCMonth: () => number ; getUTCSeconds: () => number ; setDate: (date: number) => number ; setFullYear: (year: number, month?: number, date?: number) => number ; setHours: (hours: number, min?: number, sec?: number, ms?: number) => number ; setMilliseconds: (ms: number) => number ; setMinutes: (min: number, sec?: number, ms?: number) => number ; setMonth: (month: number, date?: number) => number ; setSeconds: (sec: number, ms?: number) => number ; setTime: (time: number) => number ; setUTCDate: (date: number) => number ; setUTCFullYear: (year: number, month?: number, date?: number) => number ; setUTCHours: (hours: number, min?: number, sec?: number, ms?: number) => number ; setUTCMilliseconds: (ms: number) => number ; setUTCMinutes: (min: number, sec?: number, ms?: number) => number ; setUTCMonth: (month: number, date?: number) => number ; setUTCSeconds: (sec: number, ms?: number) => number ; toDateString: () => string ; toISOString: () => string ; toJSON: (key?: any) => string ; toLocaleDateString: () => string(locales?: string | string[], options?: DateTimeFormatOptions) => string(locales?: LocalesArgument, options?: DateTimeFormatOptions) => string ; toLocaleString: () => string(locales?: string | string[], options?: DateTimeFormatOptions) => string(locales?: LocalesArgument, options?: DateTimeFormatOptions) => string ; toLocaleTimeString: () => string(locales?: string | string[], options?: DateTimeFormatOptions) => string(locales?: LocalesArgument, options?: DateTimeFormatOptions) => string ; toString: () => string ; toTimeString: () => string ; toUTCString: () => string ; valueOf: () => number }

Name	Type
`date (optional)`	`string` \| `number` \| { `getVarDate`: () => `VarDate` ; `[toPrimitive]`: (`hint`: `"default"`) => `string`(`hint`: `"string"`) => `string`(`hint`: `"number"`) => `number`(`hint`: `string`) => `string` \| `number` ; `getDate`: () => `number` ; `getDay`: () => `number` ; `getFullYear`: () => `number` ; `getHours`: () => `number` ; `getMilliseconds`: () => `number` ; `getMinutes`: () => `number` ; `getMonth`: () => `number` ; `getSeconds`: () => `number` ; `getTime`: () => `number` ; `getTimezoneOffset`: () => `number` ; `getUTCDate`: () => `number` ; `getUTCDay`: () => `number` ; `getUTCFullYear`: () => `number` ; `getUTCHours`: () => `number` ; `getUTCMilliseconds`: () => `number` ; `getUTCMinutes`: () => `number` ; `getUTCMonth`: () => `number` ; `getUTCSeconds`: () => `number` ; `setDate`: (`date`: `number`) => `number` ; `setFullYear`: (`year`: `number`, `month?`: `number`, `date?`: `number`) => `number` ; `setHours`: (`hours`: `number`, `min?`: `number`, `sec?`: `number`, `ms?`: `number`) => `number` ; `setMilliseconds`: (`ms`: `number`) => `number` ; `setMinutes`: (`min`: `number`, `sec?`: `number`, `ms?`: `number`) => `number` ; `setMonth`: (`month`: `number`, `date?`: `number`) => `number` ; `setSeconds`: (`sec`: `number`, `ms?`: `number`) => `number` ; `setTime`: (`time`: `number`) => `number` ; `setUTCDate`: (`date`: `number`) => `number` ; `setUTCFullYear`: (`year`: `number`, `month?`: `number`, `date?`: `number`) => `number` ; `setUTCHours`: (`hours`: `number`, `min?`: `number`, `sec?`: `number`, `ms?`: `number`) => `number` ; `setUTCMilliseconds`: (`ms`: `number`) => `number` ; `setUTCMinutes`: (`min`: `number`, `sec?`: `number`, `ms?`: `number`) => `number` ; `setUTCMonth`: (`month`: `number`, `date?`: `number`) => `number` ; `setUTCSeconds`: (`sec`: `number`, `ms?`: `number`) => `number` ; `toDateString`: () => `string` ; `toISOString`: () => `string` ; `toJSON`: (`key?`: `any`) => `string` ; `toLocaleDateString`: () => `string`(`locales?`: `string` \| `string`[], `options?`: `DateTimeFormatOptions`) => `string`(`locales?`: `LocalesArgument`, `options?`: `DateTimeFormatOptions`) => `string` ; `toLocaleString`: () => `string`(`locales?`: `string` \| `string`[], `options?`: `DateTimeFormatOptions`) => `string`(`locales?`: `LocalesArgument`, `options?`: `DateTimeFormatOptions`) => `string` ; `toLocaleTimeString`: () => `string`(`locales?`: `string` \| `string`[], `options?`: `DateTimeFormatOptions`) => `string`(`locales?`: `LocalesArgument`, `options?`: `DateTimeFormatOptions`) => `string` ; `toString`: () => `string` ; `toTimeString`: () => `string` ; `toUTCString`: () => `string` ; `valueOf`: () => `number` }

Returns

Date

constructError

▸ constructError(...constructorArguments): Error

Functional alias for new Error().

Parameters

Name	Type
`...constructorArguments`	[message?: string, options?: ErrorOptions]

Returns

Error

constructIntlCollator

▸ constructIntlCollator(...constructorArguments): Collator

Functional alias for new Intl.Collator(), which enables language-sensitive string comparison.

Parameters

Name	Type
`...constructorArguments`	[locales?: string \| string[], options?: CollatorOptions]

Returns

Collator

See

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Collator

constructIntlDateTimeFormat

▸ constructIntlDateTimeFormat(...constructorArguments): DateTimeFormat

Functional alias for new Intl.DateTimeFormat(), which enables language-sensitive date and time formatting.

Parameters

Name	Type
`...constructorArguments`	[locales?: string \| string[], options?: DateTimeFormatOptions]

Returns

DateTimeFormat

See

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat

constructIntlLocale

▸ constructIntlLocale(tag, options?): Locale

Functional alias for new Intl.Locale(), which represents a Unicode locale identifier.

Parameters

Name	Type	Description
`tag`	`ReadOnly`<`Locale` \| `LocaleIdentifier`>	-
`options (optional)`	`Object`	-
`options.baseName (optional)`	`string`	A string containing the language, and the script and region if available.
`options.calendar (optional)`	`string`	The part of the Locale that indicates the locale’s calendar era.
`options.caseFirst (optional)`	`LocaleCollationCaseFirst`	Flag that defines whether case is taken into account for the locale’s collation rules.
`options.collation (optional)`	`string`	The collation type used for sorting
`options.hourCycle (optional)`	`LocaleHourCycleKey`	The time keeping format convention used by the locale.
`options.language (optional)`	`string`	The primary language subtag associated with the locale.
`options.numberingSystem (optional)`	`string`	The numeral system used by the locale.
`options.numeric (optional)`	`boolean`	Flag that defines whether the locale has special collation handling for numeric characters.
`options.region (optional)`	`string`	The region of the world (usually a country) associated with the locale. Possible values are region codes as defined by ISO 3166-1.
`options.script (optional)`	`string`	The script used for writing the particular language used in the locale. Possible values are script codes as defined by ISO 15924.

Returns

Locale

See

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Locale

constructIntlNumberFormat

▸ constructIntlNumberFormat(...constructorArguments): NumberFormat

Functional alias for new Intl.NumberFormat(), which enables language-sensitive number formatting.

Parameters

Name	Type
`...constructorArguments`	[locales?: string \| string[], options?: NumberFormatOptions]

Returns

NumberFormat

See

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat

constructIntlPluralRules

▸ constructIntlPluralRules(...constructorArguments): PluralRules

Functional alias for new Intl.PluralRules(), which enables plural-sensitive formatting and plural-related language rules.

Parameters

Name	Type
`...constructorArguments`	[locales?: string \| string[], options?: PluralRulesOptions]

Returns

PluralRules

See

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/PluralRules

constructIntlRelativeTimeFormat

▸ constructIntlRelativeTimeFormat(...constructorArguments): RelativeTimeFormat

Functional alias for new Intl.RelativeTimeFormat(), which enables language-sensitive relative time formatting.

Parameters

Name	Type
`...constructorArguments`	[locales?: string \| string[], options?: RelativeTimeFormatOptions]

Returns

RelativeTimeFormat

See

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat

constructMap

▸ constructMap<Key, Value>(iterable?): Map<Key, Value>

Functional alias for new Map().

Type parameters

Name
`Key`
`Value`

Parameters

Name	Type
`iterable (optional)`	`Iterable`<readonly [`Key`, `Value`]>

Returns

Map<Key, Value>

constructPromise

▸ constructPromise<Value>(executor): Promise<Value>

Functional alias for new Promise().

Type parameters

Name
`Value`

Parameters

Name	Type
`executor`	(`resolve`: (`value`: `Value`) => `void`, `reject`: (`reason?`: `unknown`) => `void`) => `void`

Returns

Promise<Value>

constructProxy

▸ constructProxy<Target>(target, handler): Target

Functional alias for new Proxy().

Type parameters

Name	Type
`Target`	extends `object`

Parameters

Name	Type
`target`	`Target`
`handler`	`ProxyHandler`<`Target`>

Returns

Target

constructRangeError

▸ constructRangeError(...constructorArguments): Error

Functional alias for new RangeError().

Parameters

Name	Type
`...constructorArguments`	[message?: string, options?: ErrorOptions]

Returns

Error

constructReferenceError

▸ constructReferenceError(...constructorArguments): Error

Functional alias for new ReferenceError().

Parameters

Name	Type
`...constructorArguments`	[message?: string, options?: ErrorOptions]

Returns

Error

constructRegExp

▸ constructRegExp(...constructorArguments): RegExp

Functional alias for new RegExp().

Parameters

Name	Type
`...constructorArguments`	[pattern: string \| RegExp, flags?: string]

Returns

RegExp

constructSet

▸ constructSet<Value>(iterable?): Set<Value>

Functional alias for new Set().

Type parameters

Name
`Value`

Parameters

Name	Type
`iterable (optional)`	`Iterable`<`Value`>

Returns

Set<Value>

constructSyntaxError

▸ constructSyntaxError(...constructorArguments): Error

Functional alias for new SyntaxError().

Parameters

Name	Type
`...constructorArguments`	[message?: string, options?: ErrorOptions]

Returns

Error

constructTypeError

▸ constructTypeError(...constructorArguments): Error

Functional alias for new TypeError().

Parameters

Name	Type
`...constructorArguments`	[message?: string, options?: ErrorOptions]

Returns

Error

constructURIError

▸ constructURIError(...constructorArguments): Error

Functional alias for new URIError().

Parameters

Name	Type
`...constructorArguments`	[message?: string, options?: ErrorOptions]

Returns

Error

constructWeakMap

▸ constructWeakMap<Key, Value>(iterable?): WeakMap<Key, Value>

Functional alias for new WeakMap().

Type parameters

Name	Type
`Key`	extends `object`
`Value`	`Value`

Parameters

Name	Type
`iterable (optional)`	`Iterable`<readonly [`Key`, `Value`]>

Returns

WeakMap<Key, Value>

constructWeakSet

▸ constructWeakSet<Value>(iterable?): WeakSet<Value>

Functional alias for new WeakSet().

Type parameters

Name	Type
`Value`	extends `object`

Parameters

Name	Type
`iterable (optional)`	`Iterable`<`Value`>

Returns

WeakSet<Value>

Common

toString

▸ toString<Input>(input): Input extends Strigifiable ? `${Input}` : Input extends { toString: () => string } ? ReturnType<Input["toString"]> : string

Parses given value to string, if number is given, then that’s used as a radix and a function is returned expecting an actual value.

Type parameters

Name	Type
`Input`	extends `Strigifiable` \| { `toString`: () => `string` }

Parameters

Name	Type
`input`	`Input`

Returns

Input extends Strigifiable ? `${Input}` : Input extends { toString: () => string } ? ReturnType<Input["toString"]> : string

string or function expecting a value.

Example

const toDecimal = toString(10);

toDecimal(10); // "10"
toString(16)(16); // "10"
toString(2)(2); // "10"
toString({}); // "[object Object]"
toString({ toString: _ => "test" }); // "test"

Conditions

when

▸ when<Value, Predicated>(predicate): <TrueOutput>(truthyHandler: Unary<Predicated & Value, TrueOutput>) => <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: Value) => TrueOutput | FalseOutput

Curried conditional (like a functional ternary).

Type parameters

Name	Type
`Value`	`Value`
`Predicated`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Predicated`> extends `Single`<`never`> ? `Filter`<`Value`> : `Predicate`<`Value`, `Predicated`>	Predicate to check value against.

Returns

fn

Curried function with predicate in context.

▸ <TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: Value) => TrueOutput | FalseOutput

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`Predicated` & `Value`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: Value) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`Value` extends `Predicated` ? `Value` : `Predicated`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`Value`

Returns

TrueOutput | FalseOutput

Example

const isEven = (value: number) => value % 2 === 0;
const whenIsEven = when(isEven);
const double = (value: number) => value * 2;
const doubleWhenEven = whenIsEven(double);
const triple = (value: number) => value * 3;
const tripleWhenOdd = whenIsEven(triple);

tripleWhenOdd(2); // 4
tripleWhenOdd(3); // 9

whenFalsy

▸ whenFalsy<Value, Predicated>(predicate): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: Value) => Predicated & Value | FalseOutput

Like when, but when is falsy the value is returned as is.

Type parameters

Name	Type
`Value`	`Value`
`Predicated`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Predicated`> extends `Single`<`never`> ? `Filter`<`Value`> : `Predicate`<`Value`, `Predicated`>	Predicate to check value against.

Returns

fn

Curried function with predicate in context.

▸ <FalseInput, FalseOutput>(falsyHandler): (value: Value) => Predicated & Value | FalseOutput

Type parameters

Name	Type
`FalseInput`	`Value` extends `Predicated` ? `Value` : `Predicated`
`FalseOutput`	`Predicated` & `Value`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): Predicated & Value | FalseOutput

Parameters

Name	Type
`value`	`Value`

Returns

Predicated & Value | FalseOutput

Example

const isEven = (value: number) => value % 2 === 0;
const whenIsOdd = whenFalsy(isEven);
const double = (value: number) => value * 2;
const doubleWhenOdd = whenIsOdd(double);

doubleWhenOdd(2); // 2
doubleWhenOdd(3); // 6

whenIsArray

▸ whenIsArray<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is an Array.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`ReadOnlyArray`<`unknown`>, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`ReadOnlyArray`<`unknown`>
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsAsyncIterable

▸ whenIsAsyncIterable<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is an AsyncIterable.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<{ `[asyncIterator]`: () => `AsyncIterator`<`unknown`, `any`, `undefined`> }, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	{ `[asyncIterator]`: () => `AsyncIterator`<`unknown`, `any`, `undefined`> }
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsBigInt

▸ whenIsBigInt<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a BigInt.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`bigint`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`bigint`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsBoolean

▸ whenIsBoolean<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Boolean.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`boolean`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`boolean`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsDate

▸ whenIsDate<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Date.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`Date`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`Date`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsFalsy

▸ whenIsFalsy<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Falsy value.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`Falsy`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`Falsy`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsFunction

▸ whenIsFunction<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Function.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`Function`<`ReadOnlyArray`, `unknown`>, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`Function`<`ReadOnlyArray`, `unknown`>
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsIsomorphicIterable

▸ whenIsIsomorphicIterable<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is an AsynchronousIterable.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`IsomorphicIterable`<`unknown`>, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`IsomorphicIterable`<`unknown`>
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsIterable

▸ whenIsIterable<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is an Iterable.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<{ `[iterator]`: () => `Iterator`<`unknown`, `any`, `undefined`> }, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	{ `[iterator]`: () => `Iterator`<`unknown`, `any`, `undefined`> }
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsNull

▸ whenIsNull<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is null.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`null`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`null`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsNullish

▸ whenIsNullish<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Nullish value.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`Nullish`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`Nullish`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsNumber

▸ whenIsNumber<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Number.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`number`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`number`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsObject

▸ whenIsObject<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is an Object.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`object`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`object`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsPromise

▸ whenIsPromise<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Promise.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`Promise`<`unknown`>, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`Promise`<`unknown`>
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsPropertyKey

▸ whenIsPropertyKey<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a PropertyKey.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`PropertyKey`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`PropertyKey`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsPrototypeOfObject

▸ whenIsPrototypeOfObject<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: object) => TrueOutput | FalseOutput

Conditional handler for when something has an Object prototype.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`never`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: object) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`never`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`object`

Returns

TrueOutput | FalseOutput

whenIsRegExp

▸ whenIsRegExp<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a RegExp.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`RegExp`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`RegExp`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsSafeInteger

▸ whenIsSafeInteger<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: number) => TrueOutput | FalseOutput

Conditional handler for when a number is a SafeInteger.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`never`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: number) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`never`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`number`

Returns

TrueOutput | FalseOutput

whenIsString

▸ whenIsString<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a String.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`string`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`string`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsSymbol

▸ whenIsSymbol<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Symbol.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`symbol`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`symbol`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsTruthy

▸ whenIsTruthy<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is a Truthy value.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`unknown`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`unknown`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenIsUndefined

▸ whenIsUndefined<TrueOutput>(truthyHandler): <FalseInput, FalseOutput>(falsyHandler: Unary<FalseInput, FalseOutput>) => (value: unknown) => TrueOutput | FalseOutput

Conditional handler for when something is undefined.

Type parameters

Name
`TrueOutput`

Parameters

Name	Type
`truthyHandler`	`Unary`<`undefined`, `TrueOutput`>

Returns

fn

▸ <FalseInput, FalseOutput>(falsyHandler): (value: unknown) => TrueOutput | FalseOutput

Type parameters

Name	Type
`FalseInput`	`undefined`
`FalseOutput`	`TrueOutput`

Parameters

Name	Type
`falsyHandler`	`Unary`<`FalseInput`, `FalseOutput`>

Returns

fn

▸ (value): TrueOutput | FalseOutput

Parameters

Name	Type
`value`	`unknown`

Returns

TrueOutput | FalseOutput

whenTruthy

▸ whenTruthy<Value, Predicated>(predicate): <Output>(truthyHandler: Unary<Predicated & Value, Output>) => (value: Value) => Value | Output

Like when, but when is falsy the value is returned as is.

Type parameters

Name	Type
`Value`	`Value`
`Predicated`	`never`

Parameters

Name	Type	Description
`predicate`	`Single`<`Predicated`> extends `Single`<`never`> ? `Filter`<`Value`> : `Predicate`<`Value`, `Predicated`>	Predicate to check value against.

Returns

fn

Curried function with predicate in context.

▸ <Output>(truthyHandler): (value: Value) => Value | Output

Type parameters

Name
`Output`

Parameters

Name	Type
`truthyHandler`	`Unary`<`Predicated` & `Value`, `Output`>

Returns

fn

▸ (value): Value | Output

Parameters

Name	Type
`value`	`Value`

Returns

Value | Output

Example

const isEven = (value: number) => value % 2 === 0;
const whenIsEven = whenTruthy(isEven);
const double = (value: number) => value * 2;
const doubleWhenEven = whenIsEven(double);

doubleWhenEven(2); // 4
doubleWhenEven(3); // 3

Functions

always

▸ always<Input>(input): () => Input

Returns a function that always returns the same value.

Type parameters

Name
`Input`

Parameters

Name	Type
`input`	`Input`

Returns

fn

Function that always return the given value.

▸ (): Input

Returns

Input

Example

const alwaysFoo = always("foo");
const fillWithFoo = map(alwaysFoo);

fillWithFoo([0, 1, 2]); // ["foo", "foo", "foo"]

applyTo

▸ applyTo<Input>(input): <Output>(unary: Unary<Input, Output>) => Output

Takes a value and applies a function to it.

Type parameters

Name
`Input`

Parameters

Name	Type
`input`	`Input`

Returns

fn

Function that expects a function that will receive the input.

▸ <Output>(unary): Output

Type parameters

Name
`Output`

Parameters

Name	Type
`unary`	`Unary`<`Input`, `Output`>

Returns

Output

Example

const applyTo10 = applyTo(10);

applyTo10((value: number) => value * 2); // 20
applyTo10((value: number) => value / 2); // 5

entryKey

▸ entryKey<InputEntry>(entry): EntryKey<InputEntry>

Get key of an Entry.

Type parameters

Name	Type
`InputEntry`	extends `Entry`

Parameters

Name	Type	Description
`entry`	`InputEntry`	Entry to get key from.

Returns

EntryKey<InputEntry>

Key of an Entry.

Example

entryKey(["key", "value"]); // "key"

entryValue

▸ entryValue<InputEntry>(entry): EntryValue<InputEntry>

Get value of an Entry.

Type parameters

Name	Type
`InputEntry`	extends `Entry`

Parameters

Name	Type	Description
`entry`	`InputEntry`	Entry to get vale from.

Returns

EntryValue<InputEntry>

Value of an Entry.

Example

entryKey(["key", "value"]); // "value"

flip

▸ flip<UnaryToFlip>(unary): (…secondArgument: Parameters<UnaryOutput<UnaryToFlip>>) => (…firstArgument: Parameters<UnaryToFlip>) => UnaryOutput<UnaryOutput<UnaryToFlip>>

Flips arguments of a curried function.

Type parameters

Name	Type
`UnaryToFlip`	extends `Unary`<`never`, `Unary`<`never`, `unknown`>>

Parameters

Name	Type
`unary`	`UnaryToFlip`

Returns

fn

Curried function with unary in context.

▸ (...secondArgument): (…firstArgument: Parameters<UnaryToFlip>) => UnaryOutput<UnaryOutput<UnaryToFlip>>

Parameters

Name	Type
`...secondArgument`	`Parameters`<`UnaryOutput`<`UnaryToFlip`>>

Returns

fn

▸ (...firstArgument): UnaryOutput<UnaryOutput<UnaryToFlip>>

Parameters

Name	Type
`...firstArgument`	`Parameters`<`UnaryToFlip`>

Returns

UnaryOutput<UnaryOutput<UnaryToFlip>>

Example

const concat = (first: string) => (second: string) => `${first}${second}`;
const flippedConcat = flip(concat);

flippedConcat("1")("2"); // "21"

identity

▸ identity<Input>(input): Input

Identity function.

Type parameters

Name
`Input`

Parameters

Name	Type
`input`	`Input`

Returns

Input

Same value given.

Example

identity("foo"); // "foo"

memoize

▸ memoize<MemoizedFunction>(unary): MemoizedFunction

Memoize function return values for expensive operations.

Type parameters

Name	Type
`MemoizedFunction`	extends `Unary`<`never`, `unknown`>

Parameters

Name	Type	Description
`unary`	`MemoizedFunction`	Function to memoize.

Returns

MemoizedFunction

Curried function with unary in context.

Example

const expensiveOperation = (value: number) => value * 2;
const memoizedOperation = memoize(expensiveOperation);

memoizedOperation(2); // 4
memoizedOperation(2); // 4 (cached)

negate

▸ negate<Item, Predicated>(predicate): Single<Predicated> extends Single<never> ? Unary<Item, boolean> : Predicate<Item, Exclude<Item, Predicated>>

Takes a function and returns a copy with negated output.

Type parameters

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

Parameters

Name	Type	Description
`predicate`	`Single`<`Predicated`> extends `Single`<`never`> ? `Filter`<`Item`> : `Predicate`<`Item`, `Predicated`>	Function to be negated.

Returns

Single<Predicated> extends Single<never> ? Unary<Item, boolean> : Predicate<Item, Exclude<Item, Predicated>>

Source function with negated output.

Example

const isPositive = (value: number) => value >= 0;
const isNegative = not(isPositive);

isPositive(1); // true
isNegative(1); // false

once

▸ once<OnceFunction>(unary): (value: UnaryInput<OnceFunction>) => UnaryOutput<OnceFunction> | UnaryOutput<OnceFunction>

Runs a function once, and after that returns always the same value.

Type parameters

Name	Type
`OnceFunction`	extends `Unary`<`never`, `unknown`>

Parameters

Name	Type	Description
`unary`	`OnceFunction`	Function to run once.

Returns

fn

Curried function with unary in context.

▸ (value): UnaryOutput<OnceFunction> | UnaryOutput<OnceFunction>

Parameters

Name	Type
`value`	`UnaryInput`<`OnceFunction`>

Returns

UnaryOutput<OnceFunction> | UnaryOutput<OnceFunction>

Example

const expensiveOperation = (value: number) => value * 2;
const onceOperation = once(expensiveOperation);

onceOperation(2); // 4
onceOperation(3); // 4 (cached)

tap

▸ tap<Input>(tapper): <Tapped>(tapped: Tapped) => Tapped

Tap into a value before calling a function.

Type parameters

Name
`Input`

Parameters

Name	Type	Description
`tapper`	`Unary`<`Input`, `unknown`>	Tapper function to be called with the value.

Returns

fn

Curried function with tapper in context.

▸ <Tapped>(tapped): Tapped

Type parameters

Name	Type
`Tapped`	extends `Unary`<`Input`, `unknown`>

Parameters

Name	Type
`tapped`	`Tapped`

Returns

Tapped

Example

const log = tap(console.log);
const double = (value: number) => value * 2;
const doubleAndLog = log(double);

doubleAndLog(2); // 4 (returns and logs 4)

thunk

▸ thunk<Input, Output>(unary): (input: Input) => () => Output

Delayed evaluation function.

Type parameters

Name
`Input`
`Output`

Parameters

Name	Type
`unary`	`Unary`<`Input`, `Output`>

Returns

fn

Function that will run the given function when called.

▸ (input): () => Output

Parameters

Name	Type
`input`	`Input`

Returns

fn

▸ (): Output

Returns

Output

Example

const always = thunk(id);
const alwaysFoo = always("foo");
alwaysFoo(); // "foo"

Objects

awaitableHandler

▸ awaitableHandler<Value, Output>(handler): <AwaitableValue>(awaitable: AwaitableValue) => AwaitableValue extends Promise<Value> ? Promise<Output> : Output

If the given value is a promise, the handler is called when is resolved, otherwise the handler is called directly with the value.

Type parameters

Name
`Value`
`Output`

Parameters

Name	Type	Description
`handler`	(`awaitable`: `Value`) => `Output`	Handler function to be called with the value.

Returns

fn

Curried function with handler in context.

▸ <AwaitableValue>(awaitable): AwaitableValue extends Promise<Value> ? Promise<Output> : Output

Type parameters

Name
`AwaitableValue`

Parameters

Name	Type
`awaitable`	`AwaitableValue`

Returns

AwaitableValue extends Promise<Value> ? Promise<Output> : Output

Example

const double = maybePromiseHandler((value: number) => value * 2);

double(2); // 4
double(Promise.resolve(2)); // Promise<4>

get

▸ get<Key>(key): <Source>(object: Source) => Source[Key & keyof Source]

Get the value of a property in an object.

Type parameters

Name	Type
`Key`	extends `PropertyKey`

Parameters

Name	Type
`key`	`Key`

Returns

fn

Curried function with key in context.

▸ <Source>(object): Source[Key & keyof Source]

Type parameters

Name	Type
`Source`	extends readonly [] \| readonly [`unknown`, `unknown`] \| `Record`<`Key`, `unknown`> \| `Readonly`<`ReadonlyMap`<`unknown`, `unknown`>> \| `Readonly`<`ReadonlySet`<`unknown`>> \| readonly `unknown`[] \| `Function` & `Record`<`Key`, `unknown`> \| { readonly [Property in PropertyKey]: ReadOnly<Record<Key, unknown>[Property]> }

Parameters

Name	Type
`object`	`Source`

Returns

Source[Key & keyof Source]

Example

const getFoo = get("foo");

getFoo({ foo: "bar" }); // "bar"
getFoo({}); // undefined

mutate

▸ mutate<Update>(update): <Target>(target: Target) => Target & Update

Function to encapsulate object mutations.

Type parameters

Name	Type
`Update`	extends `object`

Parameters

Name	Type	Description
`update`	`Update`	Update to apply to given target.

Returns

fn

Curried function with update in context.

▸ <Target>(target): Target & Update

Type parameters

Name	Type
`Target`	extends `object`

Parameters

Name	Type
`target`	`Target`

Returns

Target & Update

Example

const state = { a: 1 };
mutate(set("a")(2))(state);
console.log(state); // { a: 2 }

omit

▸ omit<Properties>(...properties): <Source>(object: Source) => Omit<Source, Properties[number]>

Omits given properties from an object.

Type parameters

Name	Type
`Properties`	extends `ReadOnlyArray`<`PropertyKey`>

Parameters

Name	Type	Description
`...properties`	`Properties`	Properties to omit.

Returns

fn

Curried function with properties in context.

▸ <Source>(object): Omit<Source, Properties[number]>

Type parameters

Name	Type
`Source`	extends `Object`

Parameters

Name	Type
`object`	`Source`

Returns

Omit<Source, Properties[number]>

Example

const object = { a: 1, b: 2, c: 3 };
const omitAC = omit("a", "c");
const result = omitAC(object); // { b: 2 }

pick

▸ pick<Properties>(...properties): <Source>(object: Source) => Pick<Source, Properties[number]>

Picks given properties from an object.

Type parameters

Name	Type
`Properties`	extends `ReadOnlyArray`<`PropertyKey`>

Parameters

Name	Type	Description
`...properties`	`Properties`	Properties to pick.

Returns

fn

Curried function with properties in context.

▸ <Source>(object): Pick<Source, Properties[number]>

Type parameters

Name	Type
`Source`	extends `Object`

Parameters

Name	Type
`object`	`Source`

Returns

Pick<Source, Properties[number]>

Example

const object = { a: 1, b: 2, c: 3 };
const pickAC = pick("a", "c");
const result = pickAC(object); // { a: 1, c: 3 }

set

▸ set<Key>(key): <Value>(value: Value) => <Source>(object: Source) => Omit<Source, Key> & ReadOnlyRecord<Key, Value>

Set the value of a property in an object (read only).

Type parameters

Name	Type
`Key`	extends `PropertyKey`

Parameters

Name	Type
`key`	`Key`

Returns

fn

Curried function with key in context.

▸ <Value>(value): <Source>(object: Source) => Omit<Source, Key> & ReadOnlyRecord<Key, Value>

Type parameters

Name
`Value`

Parameters

Name	Type
`value`	`Value`

Returns

fn

▸ <Source>(object): Omit<Source, Key> & ReadOnlyRecord<Key, Value>

Type parameters

Name	Type
`Source`	extends `Object`

Parameters

Name	Type
`object`	`Source`

Returns

Omit<Source, Key> & ReadOnlyRecord<Key, Value>

Example

const setFoo = set("foo");

setFoo("baz")({ foo: "bar" }); // { foo: "baz" }
setFoo("baz")({ bar: "foo" }); // { bar: "foo", foo: "baz" }
setFoo("baz")({}); // { foo: "baz" }

Promises

otherwise

▸ otherwise<Output>(handler): <PromisedValue>(promise: Promise<PromisedValue>) => Promise<Output | PromisedValue>

Sets a promise catch handler.

Type parameters

Name
`Output`

Parameters

Name	Type
`handler`	`Unary`<`unknown`, `Output` \| `PromiseLike`<`Output`>>

Returns

fn

Curried function with handler set in context.

▸ <PromisedValue>(promise): Promise<Output | PromisedValue>

Type parameters

Name
`PromisedValue`

Parameters

Name	Type
`promise`	`Promise`<`PromisedValue`>

Returns

Promise<Output | PromisedValue>

Example

const otherwiseLog = otherwise(console.error);

otherwiseLog(fetch("/api")); // Logs on error.

then

▸ then<HandlerInput, Output>(handler): <PromiseInstance>(promise: PromiseInstance) => Promise<Output>

Sets a promise then handler.

Type parameters

Name
`HandlerInput`
`Output`

Parameters

Name	Type
`handler`	`Unary`<`HandlerInput`, `Output` \| `PromiseLike`<`Output`>>

Returns

fn

Curried function with handler set in context.

▸ <PromiseInstance>(promise): Promise<Output>

Type parameters

Name	Type
`PromiseInstance`	extends `Promise`<`HandlerInput`>

Parameters

Name	Type
`promise`	`PromiseInstance`

Returns

Promise<Output>

Example

const thenJson = then((response: Response) => response.json());

thenJson(fetch("/api")); // Parsed response