Types Reference

License NPM Version Open Issues

🏷️ Collection of TypeScript types shared across Lou Codes projects.

Usage

📦 Node

Install @lou.codes/types as a dependency:

1
pnpm add @lou.codes/types
2
# or
3
npm install @lou.codes/types
4
# or
5
yarn add @lou.codes/types

Import as type and use it:

1
import type { Unary } from "@lou.codes/types";

🦕 Deno

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

1
import type { Unary } from "npm:@lou.codes/types";

Useful links

📝 Documentation: TypeDoc generated documentation.
⏳ Changelog: List of changes between versions.

Array

ArrayLike

Ƭ ArrayLike<Item, Length>: ReadOnlyRecord<NeverFallback<Exclude<Enumerate<Length>, Length>, number>, Item> & { length: Length }

An alternative for TypeScript’s ArrayLike type, with its type set to unknown by default. It also makes it shallowly read-only.

Remarks

When working with optional types, having to type ArrayLike<unknown> every time gets annoying pretty fast. This type is a drop-in replacement for ArrayLike, with the only difference being that the type of the items is set to unknown by default.

Example

1
const arrayLike: ArrayLike<number> = [1, 2, 3];

Type parameters

Name	Type	Description
`Item`	`unknown`	Type of the items in the array-like object.
`Length`	extends `number` = `number`	-

Empty

Ƭ Empty: EmptyArray | EmptyRecord | EmptyString

Empty array, object or string.

Remarks

Union type of EmptyArray, EmptyRecord and EmptyString, to signify values that are empty.

Example

1
const emptyString: Empty = "";
2
const emptyArray: Empty = [];
3
const emptyRecord: Empty = {};

See

EmptyArray
EmptyRecord
EmptyString

EmptyArray

Ƭ EmptyArray: typeof EMPTY_ARRAY

Empty array.

Remarks

This is a type alias for an readonly empty array. Trying to access items on it will give a compile-time error.

Example

1
const emptyArray: EmptyArray = [];

Entry

Ƭ Entry<Key, Value>: readonly [key: Key, value: Value]

Entry couple [key, value].

Remarks

It is a tuple of two elements, the first one being the key and the second one being the value of an object’s property.

Example

1
const entry: Entry<string, number> = ["🟢", 1];

Type parameters

Name	Type	Description
`Key`	`PropertyKey`	Object’s properties type.
`Value`	`unknown`	Object’s values type.

EntryKey

Ƭ EntryKey<Input>: Input[0]

Key of an Entry.

Remarks

Util type to get the key of an Entry.

Example

1
const entry: Entry<string, number> = ["🟢", 1];
2
const entryKey: EntryKey<typeof entry> = entry[0];

See

Entry

Type parameters

Name	Type	Description
`Input`	extends `Entry`	Entry type.

EntryOf

Ƭ EntryOf<Type>: Entry<KeyOf<Type>, ValueOf<Type>>

Object or array Entry.

Remarks

Get the Entry type out of an object or array.

Example

1
const object = {
2
	"🟢": 1,
3
	"🟩": 2,
4
};
5
const entries: EntryOf<typeof object> = Object.entries(object)[0];

See

Entry
KeyOf
ValueOf

Type parameters

Name	Type	Description
`Type`	extends `object`	Object or array type.

EntryValue

Ƭ EntryValue<Input>: Input[1]

Value of an Entry.

Remarks

Util type to get the value of an Entry.

Example

1
const entry: Entry<string, number> = ["🟢", 1];
2
const entryValue: EntryValue<typeof entry> = entry[1];

See

Entry

Type parameters

Name	Type	Description
`Input`	extends `Entry`	Entry type.

Head

Ƭ Head<Input>: HeadAndTail<Input>[0]

Initial value of an ArrayLike.

Remarks

Given a type argument (an ArrayLike), this returns the type of the item in index 0.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const head: Head<typeof array> = "🟢";

See

ArrayLike
HeadAndTail

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	`ArrayLike` value (such as `Array` or `string`).

HeadAndTail

Ƭ HeadAndTail<Input>: Input extends readonly [head: infer HeadItem, tail: infer TailItems] ? readonly [head: HeadItem, tail: TailItems] : Input extends `${infer FirstCharacter}${infer RestOfString}` ? readonly [head: FirstCharacter, tail: RestOfString] : Input extends EmptyArray | EmptyString ? readonly [head: undefined, tail: Input] : readonly [head: Maybe<Input[number]>, tail: Input]

Get a couple with the head and tail types of an ArrayLike.

Remarks

Given a type argument (an ArrayLike), this returns a couple with the type of the item in index 0 first, and the rest of the ArrayLike after.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const headAndTail: HeadAndTail<typeof array> = ["🟢", ["🟩", "💚"]];

See

ArrayLike
EmptyArray
EmptyString
Head
Maybe
Tail

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	Input `ArrayLike`.

Initial

Ƭ Initial<Input>: InitialAndLast<Input>[0]

Initial values of an ArrayLike (omitting the last).

Remarks

Given a type argument (an ArrayLike), this returns the type of the items from the start of the ArrayLike until the before to last item.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const initial: Initial<typeof array> = ["🟢", "🟩"];

See

ArrayLike
InitialAndLast

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	`ArrayLike` value (such as `Array` or `string`).

InitialAndLast

Ƭ InitialAndLast<Input>: Input extends readonly […(infer InitialItems), infer LastItem] ? readonly [initial: InitialItems, last: LastItem] : Input extends EmptyArray | EmptyString ? readonly [initial: Input, last: undefined] : Input extends `${infer FirstCharacter}${infer RestOfString}` ? readonly [initial: `${RestOfString extends EmptyString ? EmptyString : FirstCharacter}${Head<InitialAndLast<RestOfString>>}`, last: `${RestOfString extends EmptyString ? FirstCharacter : Last<RestOfString>}`] : readonly [initial: Input, last: Maybe<Input[number]>]

Get a couple with the initial and last types of an ArrayLike.

Remarks

Given a ArrayLike, this returns a couple with the type of all items from the start until the item before last, and then the last.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const initialAndLast: InitialAndLast<typeof array> = [["🟢", "🟩"], "💚"];

See

ArrayLike
EmptyArray
EmptyString
Head
Initial
Last
Maybe

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	Input `ArrayLike`.

KeyOf

Ƭ KeyOf<Type>: Type extends ArrayLike ? NeverFallback<Just<Exclude<Partial<Type>["length"], Type["length"]>>, number> : `${Exclude<keyof Type, symbol>}`

Generic key for either object or array.

Remarks

Type to represent the type of the key in an array or object. It automatically omits symbol keys from objects, and uses number for arrays with dynamic length.

Example

1
const array = [1, 2, 3] as const;
2
const object = { "🟢": "🟩" } as const;
3

4
const arrayKey: KeyOf<typeof array> = 0;
5
const objectKey: KeyOf<typeof object> = "🟢";

Type parameters

Name	Type	Description
`Type`	extends `object`	Object or array type.

Last

Ƭ Last<Input>: InitialAndLast<Input>[1]

Last value of an ArrayLike.

Remarks

Type of the last character of a string or the last element of an array.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const last: Last<typeof array> = "💚";

See

ArrayLike
InitialAndLast

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	The input `ArrayLike`.

MaybeEmpty

Ƭ MaybeEmpty<Input>: Either<Input, Input extends ReadOnlyArray ? EmptyArray : Input extends string ? EmptyString : Input extends ReadOnlyRecord ? EmptyRecord : undefined>

Creates an union of the given type with a possible “empty” value.

Remarks

This type is useful to make clear that we expect a possible empty value.

Example

1
type Greet: MaybeEmpty<"Hello">; // "Hello" | ""
2
type Triple: MaybeEmpty<readonly [1, 2, 3]>; // readonly [1, 2, 3] | readonly []
3
type Foo: MaybeEmpty<{ readonly foo: "bar" }>; // { readonly foo: "bar" } | {}

See

Either
EmptyArray
EmptyRecord
EmptyString

Type parameters

Name	Description
`Input`	Type to unite with it’s empty counterpart.

NotEmpty

Ƭ NotEmpty<Type>: Exclude<Type, Empty>

Type for a non-empty ArrayLike, object or string.

Remarks

This type is useful for cases where you want to ensure that a value is not empty. For example, if you have an array that should always have at least one element, you could type it as NotEmpty<ArrayLike<ElementType>>.

Example

1
const notEmptyString: NotEmpty<string> = "🟢";
2
const notEmptyArray: NotEmpty<ReadOnlyArray> = ["🟢", "🟩"];
3
const notEmptyRecord: NotEmpty<ReadOnlyRecord> = { "🟢": "🟩" };

See

Empty

Type parameters

Name	Type	Description
`Type`	extends `ArrayLike` \| `object` \| `string`	The type to check.

ReadOnlyArray

Ƭ ReadOnlyArray<Item>: ReadonlyArray<Item>

An alternative for TypeScript’s ReadonlyArray type, with its type set to unknown by default.

Remarks

There’s already a native ReadonlyArray type, but this type has a default type parameter to make it easier to use when the type of an array is unknown.

Example

1
const array: ReadOnlyArray<{ "🟢": number }> = [{ "🟢": 1 }, { "🟢": 2 }];
2
array[0]["🟢"] = 3; // Error

Type parameters

Name	Type	Description
`Item`	`unknown`	Type of the items in the array.

Reducer

Ƭ Reducer<Item, Accumulator>: Unary<Item, Unary<Accumulator, Accumulator>>

Reducer/Folder function.

Remarks

Type to represent a folder/reducer unary function that takes an item and an accumulator something of the type of the accumulator.

Example

1
const reducer: Reducer<number, number> = item => accumulator =>
2
	accumulator + item;

See

Unary

Type parameters

Name	Description
`Item`	Type of the items to reduce.
`Accumulator`	Type of the accumulator/output.

Tail

Ƭ Tail<Input>: HeadAndTail<Input>[1]

Last values of an ArrayLike (omitting the first).

Remarks

Type of the last items of an ArrayLike, excluding the first item in said ArrayLike.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const tail: Tail<typeof array> = ["🟩", "💚"];

See

ArrayLike
HeadAndTail

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	Type of the array to get the tail.

ValueOf

Ƭ ValueOf<Type>: KeyOf<Type> extends keyof Type ? Type[KeyOf<Type>] : never

Generic key for either object or array.

Remarks

This type is used to get the type of the values in a collection (items of an ArrayLike or properties of a Record).

Example

1
const object = {
2
	"🟢": 1,
3
	"🟩": 2,
4
};
5
const key: ValueOf<typeof object> = 1;

See

KeyOf

Type parameters

Name	Type	Description
`Type`	extends `object`	Object or array type.

Common

Awaitable

Ƭ Awaitable<Type>: PromiseLike<Type> | Type

A value that might be coming from a Promise.

Remarks

Union type useful when you want to accept both Promise and non-Promise for a given type, both “awaitable”.

Example

1
type AwaitableString = Awaitable<string>;
2
const promisedValue: AwaitableString = Promise.resolve("🟢");
3
const plainValue: AwaitableString = "🟩";
4

5
Promise.all([promisedValue, plainValue]).then(console.log); // ["🟢", "🟩"]

See

Promise

Type parameters

Name	Type	Description
`Type`	`unknown`	The type to await.

Either

Ƭ Either<Right, Left>: Right | Left

Value that can be something or something else.

Remarks

Union type useful for cases where a value might be of one type or another. By convention we use Right for the “success” type and Left for the error.

Example

1
type MaybeNumber = Either<number, string>;
2
const maybeNumber: MaybeNumber = 1;
3
const notNumber: MaybeNumber = "1";

Type parameters

Name	Description
`Right`	The “correct” type.
`Left`	The “error” type.

Falsy

Types that evaluates to false in JS.

Remarks

Union type of the values that evaluate to false in JavaScript. Due to TypeScript type limitations NaN can’t be included.

Example

1
const falsyBoolean: Falsy = false;
2
const falsyHTMLAllCollection: Falsy = document.all;
3
const falsyNegativeZero: Falsy = -0;
4
const falsyNegativeZeroBigInt: Falsy = -0n;
5
const falsyNull: Falsy = null;
6
const falsyString: Falsy = "";
7
const falsyUndefined: Falsy = undefined;
8
const falsyZero: Falsy = 0;
9
const falsyZeroBigInt: Falsy = 0n;

See

JSONValue

Ƭ JSONValue: Exclude<Primitive, bigint | symbol | undefined> | ReadonlyArray<JSONValue> | { [property: string]: JSONValue; }

Possible parsed JSON value.

Remarks

Following the JSON specification, the result of a JSON.parse call can be one of a given set of types. This type is a union of all of those types.

Example

1
const json: JSONValue = JSON.parse('{"foo": "bar"}');

See

JSON

Just

Ƭ Just<Input>: Exclude<Input, undefined>

Excludes undefined of a type union.

Remarks

Every now and then a type is possibly undefined, this type gets rid of the undefined in the union.

Example

1
const maybeUndefined: string | undefined = "🟢";
2
const defined: Just<typeof maybeUndefined> = "🟢"; // ok
3
const noDefined: Just<typeof maybeUndefined> = undefined; // error

See

Maybe

Type parameters

Name
`Input`

Maybe

Ƭ Maybe<Input>: Either<Just<Input>, undefined>

Value that can be undefined.

Remarks

Union type useful for cases where a value might be undefined, and provides a simple way to express this in TypeScript. For example, the return type of a function that returns a string or undefined could be typed as Maybe<string>.

Example

1
type MaybeNumber = Maybe<number>;
2
const maybeNumber: MaybeNumber = 1;
3
const notNumber: MaybeNumber = undefined;

See

Just

Type parameters

Name	Description
`Input`	The type of the value to make optional.

NeverFallback

Ƭ NeverFallback<MaybeNever, Fallback>: Single<MaybeNever> extends Single<never> ? Fallback : MaybeNever

Takes a value that could be never, and if it is never it goes to the Fallback value.

Remarks

There are some scenarios where a value can end up being of type never, this works sorta like the the ?? operator, but for never.

Example

1
const value: never = undefined as never;
2
NeverFallback<typeof value, number>; // Will be number

See

Single

Type parameters

Name	Description
`MaybeNever`	The type that may or may not be `never`.
`Fallback`	The fallback type to use if `MaybeNever` is `never`.

Nullish

Ƭ Nullish: Maybe<null>

Nullish value (either null or undefined).

Remarks

This type is useful for cases where a value might be null or undefined, generally meant to be dealt with using the ?? operator.

Example

1
const nullishUndefined: Nullish = undefined;
2
const nullishNull: Nullish = null;

See

Primitive

Ƭ Primitive: Nullish | Numeric | boolean | string | symbol

Valid JavaScript primitives.

Remarks

This type is a union of all the valid JavaScript primitives, including null, undefined, boolean, number, bigint, string, and symbol.

Example

1
const aBigInt: Primitive = 13n;
2
const aBoolean: Primitive = true;
3
const aNull: Primitive = null;
4
const aNumber: Primitive = 13;
5
const anUndefined: Primitive = undefined;
6
const aString: Primitive = "🟢";
7
const aSymbol: Primitive = Symbol("🟢");

See

Nullish
Numeric
Primitive

Replace

Ƭ Replace<Type, Keys, NewType>: Omit<Type, Keys> & { readonly [Property in Keys]: NewType }

Intersection that replaces the type of some keys in given object type.

Remarks

Intersection type to replace all the given keys of an object type with a new type.

Example

1
type User = { name: string; age: number };
2
type ReallyOldUser = Replace<User, "age", bigint>;

Type parameters

Name	Type	Description
`Type`	extends `object`	Type to replace the type of some keys in.
`Keys`	extends keyof `Type`	Keys to replace the type of.
`NewType`	`NewType`	New type to replace the old type with.

Single

Ƭ Single<Type>: readonly [single: Type]

Tuple of length 1 (AKA Monuple).

Remarks

Tuple with a single element on it, useful when doing optional types that compare to never.

Example

1
const single: Single<boolean> = [true];

Type parameters

Name	Description
`Type`	Type of the single element.

Strigifiable

Ƭ Strigifiable: Exclude<Primitive, symbol>

Values that can be stringified.

Remarks

Type to represent all values that can be stringified, all primitives excluding symbol: string, number, bigint, boolean, undefined, and null.

Example

1
let value: Strigifiable = "hello";
2
value = 1;
3
value = true;
4
value = Symbol("hello"); // Error!
5
value = { toString: () => "hello" }; // Error!

See

Primitive

Truthy

Ƭ Truthy<Type>: Exclude<Type, Falsy>

Excludes all Falsy values of the given Type.

Remarks

Type to represent all values of the given Type that are not Falsy. If all types are Falsy, the result is never.

Example

1
Truthy<"" | "truthy">; // "truthy"

See

Falsy

Type parameters

Name	Type	Description
`Type`	`unknown`	Type to exclude `Falsy` values from.

TypeOfDictionary

Ƭ TypeOfDictionary: Object

typeof dictionary.

Remarks

Dictionary of types and their typeof values, including the proposed but never added type "null" for null.

Example

1
TypeOfMap["string"]; // `string`
2
TypeOfMap["boolean"]; // `boolean`
3
TypeOfMap["function"]; // `GenericFunction`

See

Type declaration

Name	Type	Description
`bigint`	`bigint`	TypeOfDictionary key for `BigInt`
`boolean`	`boolean`	TypeOfDictionary key for `Boolean`
`function`	`Function`	TypeOfDictionary key for `Function`
`null`	`null`	TypeOfDictionary key for `null`
`number`	`number`	TypeOfDictionary key for `Number`
`object`	`object`	TypeOfDictionary key for `Object`
`string`	`string`	TypeOfDictionary key for `String`
`symbol`	`symbol`	TypeOfDictionary key for `Symbol`
`undefined`	`undefined`	TypeOfDictionary key for `undefined`

TypeOfValue

Ƭ TypeOfValue: KeyOf<TypeOfDictionary>

Possible type values returned by typeof.

Remarks

Type to represent the possible values returned by typeof, including the proposed but never added type "null" for null.

Example

1
const typeString: TyeOfValue = "string";
2
const typeBoolean: TyeOfValue = "boolean";
3
const typeFunction: TyeOfValue = "function";

See

Unbound

Ƭ Unbound<Type>: Type extends ReadonlyArray<infer Item> ? { [Property in keyof ReadonlyArray<Item>]: ReadonlyArray<Item>[Property] extends Function ? Function : ReadonlyArray<Item>[Property] } : { [Property in keyof Type]: Type[Property] extends Function ? Function : Type[Property] }

Type that replaces adds the this: void argument to all the methods in the given Type.

Remarks

This type is used when the unbound of all methods is automated.

Example

1
Unbound < Date > ["getTime"]; // (this: void) => number

Type parameters

Name	Type	Description
`Type`	`unknown`	Type to be unbounded.

Date

DayOfMonth

Ƭ DayOfMonth: Range<1, 31>

Day of the month values in numeric format (from 1 to 31).

Remarks

Stricter than number type for day of the month values, limited to valid values from 1 to 31, and giving type errors otherwise.

Example

1
const days: Iterable<DayOfMonth> = [1, 2, 3, 28, 29, 30, 31];

See

Enumerate
Date

DayOfWeek

Ƭ DayOfWeek: Enumerate<6>

Day of the week values in numeric format (from 0 to 6).

Remarks

Stricter than number type for day of the week values, limited to valid values from 0 to 6, and giving type errors otherwise.

Example

1
const daysOfWeek: Iterable<DayOfWeek> = [0, 1, 2, 3, 4, 5, 6];

See

Enumerate
Date

Hours

Ƭ Hours: Enumerate<23>

Hours values in numeric format (from 0 to 23).

Remarks

Stricter than number type for hour values, limited to valid values from 0 to 23, and giving type errors otherwise.

Example

1
const hours: Iterable<Hours> = [0, 1, 2, 3, 20, 21, 22, 23];

See

Enumerate
Date

ISODate

Ƭ ISODate: `${ISOYear}-${ISOMonth}-${ISODayOfMonth}T${MultiDigitNumberString}:${MultiDigitNumberString}:${MultiDigitNumberString}.${MultiDigitNumberString}Z`

String representing an ISO date.

Remarks

This type is a string representing an ISO 8601 format of a date (returned by Date#toISOString). It uses MultiDigitNumberString because the type complexity using better types is too hight.

Example

1
const date: ISODate = "2020-01-01T00:00:00.000Z";

See

ISODayOfMonth

Ƭ ISODayOfMonth: `0${Exclude<Digit, 0>}` | `${1 | 2}${Digit}` | `3${Enumerate<1>}`

Day of the month values in string format ("01" to "31").

Remarks

Union type stricter than string type for day of the month values, limited to valid values from "01" to "31", and giving type errors otherwise.

Example

1
const days: Iterable<ISODayOfMonth> = ["01", "15", "31"];

See

Digit
Enumerate
Date

ISOHours

Ƭ ISOHours: `${Enumerate<1>}${Digit}` | `2${Enumerate<3>}`

Hours values in string format (from "00" to "23").

Remarks

Union type stricter than string type for hour values, limited to valid values from "00" to "23", and giving type errors otherwise.

Example

1
const hours: Iterable<ISOHours> = ["00", "06", "23"];

See

Enumerate
Date

ISOMilliseconds

Ƭ ISOMilliseconds: `${Digit}${Digit}${Digit}`

ISO milliseconds values in string format (from "000" to "999").

Remarks

Stricter than string type for millisecond values, limited to valid values from "000" to "999", and giving type errors otherwise.

Example

1
const milliseconds: Iterable<ISOMilliseconds> = ["001", "250", "999"];

See

Date
Digit

ISOMinutes

Ƭ ISOMinutes: `${Enumerate<5>}${Digit}`

ISO minutes values in string format (from "00" to "59").

Remarks

Stricter than string type for minute values, limited to valid values from "00" to "59", and giving type errors otherwise.

Example

1
const minutes: Iterable<ISOMinutes> = ["00", "30", "59"];

See

Date
Digit
Enumerate

ISOMonth

Ƭ ISOMonth: `0${Exclude<Digit, 0>}` | `1${Enumerate<2>}`

ISO Month values in string format (from "01" to "12").

Remarks

Union type stricter than string type for month values, limited to valid values from "01" to "12", and giving type errors otherwise.

Example

1
const months: Iterable<ISOMonth> = ["01", "06", "12"];

See

Date
Digit
Enumerate

ISOSeconds

Ƭ ISOSeconds: `${Enumerate<5>}${Digit}`

ISO seconds values in string format (from "00" to "59").

Remarks

Stricter than string type for seconds values, limited to valid values from "00" to "59", and giving type errors otherwise.

Example

1
const seconds: Iterable<ISOSeconds> = ["00", "30", "59"];

See

Date
Digit
Enumerate

ISOYear

Ƭ ISOYear: `${EmptyString | “-00”}${MultiDigitNumberString}`

ISO year values in string format.

Remarks

Stricter than string type for year values, limited to valid values from "-271821" to "275760", and giving type errors otherwise.

Example

1
const years: Iterable<ISOYear> = ["2020", "-001000", "1989"];

See

Date

Milliseconds

Ƭ Milliseconds: Enumerate<999>

ISO milliseconds values in number format (from 0 to 999).

Remarks

Stricter than number type for millisecond values, limited to valid values from 0 to 999, and giving type errors otherwise.

Example

1
const milliseconds: Iterable<Milliseconds> = [1, 250, 999];

See

Date
Enumerate

Minutes

Ƭ Minutes: Enumerate<59>

ISO minutes values in number format (from 0 to 59).

Remarks

Stricter than number type for minute values, limited to valid values from 0 to 59, and giving type errors otherwise.

Example

1
const minutes: Iterable<Minutes> = [0, 30, 59];

See

Date
Enumerate

Month

Ƭ Month: Enumerate<11>

ISO Month values in number format (from 0 to 11).

Remarks

Stricter than number type for month values, limited to valid values from 0 to 11, and giving type errors otherwise.

Example

1
const months: Iterable<ISOMonth> = [1, 6, 11];

See

Date
Enumerate

Seconds

Ƭ Seconds: Enumerate<59>

ISO seconds values in number format (from 0 to 59).

Remarks

Stricter than number type for seconds values, limited to valid values from 0 to 59, and giving type errors otherwise.

Example

1
const seconds: Iterable<Seconds> = [0, 30, 59];

See

Date
Enumerate

Function

Class

Ƭ Class<Arguments, Instance>: (…constructorArguments: Arguments) => Instance

A generic type for classes.

Remarks

This type is a generic constructor function, mainly used when wrapping classes.

Example

1
const example = (AClass: Class) => new AClass("test");

See

ReadOnlyArray

Type parameters

Name	Type	Description
`Arguments`	extends `ReadOnlyArray` = `ReadOnlyArray`	Arguments of the class constructor.
`Instance`	`unknown`	Instance of the class.

Type declaration

• (...constructorArguments): Instance

Parameters

Name	Type
`...constructorArguments`	`Arguments`

Returns

Instance

Filter

Ƭ Filter<Input>: Unary<Input, boolean>

Unary function that returns a boolean.

Remarks

This type is useful for cases where a function needs to check if a certain condition holds for an input value.

Example

1
const isEven: Filter<number> = number => number % 2 === 0;

See

Param

The input value to check.

Type parameters

Name	Description
`Input`	The type of the input value.

Predicate

Ƭ Predicate<Input, Predicated>: (input: Input) => input is Predicated

Unary function that returns a boolean and infers a given type for its argument.

Remarks

This type is useful for cases where a function needs to check if a certain condition holds for an input value. For example, the type of a filtering function that filters strings in an array of strings and numbers could look like Predicate<string | number, string>.

Example

1
const isString: Predicate<number | string, string> = (
2
	numberOrString,
3
): numberOrString is string => typeof numberOrString === "string";

Type parameters

Name	Type	Description
`Input`	`Input`	The type of the input value.
`Predicated`	extends `Input` = `Input`	The subset of `Input` for which the predicate holds.

Type declaration

▸ (input): input is Predicated

Parameters

Name	Type	Description
`input`	`Input`	The input value to check.

Returns

input is Predicated

ReadOnlyArguments

Ƭ ReadOnlyArguments<Input>: Input extends (…_arguments: infer Arguments) => infer _Output ? Readonly<Arguments> : never

Read-only alternative to TypeScript’s Parameters

Remarks

This type extracts the parameters of a function as a read-only tuple, similar to Parameters, but with the added benefit of making the parameters read-only.

Example

1
const example = (_foo: string, _bar: number) => undefined;
2
type ExampleArguments = ReadOnlyArguments<typeof example>; // readonly [string, number]

See

Function
ReadOnlyArray

Type parameters

Name	Type	Description
`Input`	extends `Function`	Function to extract parameters from.

Reducer

Ƭ Reducer<Item, Accumulator>: Unary<Item, Unary<Accumulator, Accumulator>>

Reducer/Folder function.

Remarks

Type to represent a folder/reducer unary function that takes an item and an accumulator something of the type of the accumulator.

Example

1
const reducer: Reducer<number, number> = item => accumulator =>
2
	accumulator + item;

See

Unary

Type parameters

Name	Description
`Item`	Type of the items to reduce.
`Accumulator`	Type of the accumulator/output.

Tagger

Ƭ Tagger<Output, Expressions>: (templateStrings: TemplateStringsArray, …expressions: Expressions) => Output

Tag function for tagged templates.

Remarks

Type to represent a tag function for tagged templates, which takes a TemplateStringArray and any number of expressions, and returns a value of type Output (string by default).

Example

1
const intParser: Tagger<number> = strings => parseInt(strings.join(""), 10);
2
intParser`100`; // 100

See

ReadOnlyArray

Type parameters

Name	Type	Description
`Output`	`string`	Type of the output value.
`Expressions`	extends `ReadOnlyArray` = `ReadOnlyArray`	Type of the expressions.

Type declaration

▸ (templateStrings, ...expressions): Output

Parameters

Name	Type
`templateStrings`	`TemplateStringsArray`
`...expressions`	`Expressions`

Returns

Output

Unary

Ƭ Unary<Input, Output>: (input: Input) => Output

Unary function.

Remarks

Type to represent a function that takes a single argument, ideal for currying.

Example

1
const unary: Unary<number, number> = number => number + 1;

See

Function
Single

Type parameters

Name	Description
`Input`	Type of the input value.
`Output`	Type of the output value.

Type declaration

▸ (input): Output

Parameters

Name	Type
`input`	`Input`

Returns

Output

UnaryInput

Ƭ UnaryInput<UnaryFunction>: UnaryFunction extends Unary<infer Input, infer _Output> ? Input : never

Unary function input type.

Remarks

This type is used to get the input type of a Unary function.

Example

1
const unary: Unary<number, string> = number => `${number}`;
2
UnaryInput<typeof unary>; // `number`

See

Unary

Type parameters

Name	Type	Description
`UnaryFunction`	extends `Unary`<`never`, `unknown`>	Type of the unary function to get the input type of.

UnaryOutput

Ƭ UnaryOutput<UnaryFunction>: UnaryFunction extends Unary<infer _Input, infer Output> ? Output : never

Unary function output type.

Remarks

This type is used to get the output type of a Unary function.

Example

1
const unary: Unary<number, string> = number => `${number}`;
2
UnaryOutput<typeof unary>; // `string`

See

Unary

Type parameters

Name	Type	Description
`UnaryFunction`	extends `Unary`<`never`, `unknown`>	Type of the unary function to get the output type of.

HTML

HTMLElementTagAttributeMap

Ƭ HTMLElementTagAttributeMap: ReadOnlyRecord<`${string}-${string}`, HTMLElementTagGlobalAttributes> & { a: HTMLElementTagGlobalAttributes & { download?: string ; href?: string ; hreflang?: string ; ping?: string ; referrerpolicy?: string ; rel?: string ; target?: string ; type?: string } ; abbr: HTMLElementTagGlobalAttributes ; address: HTMLElementTagGlobalAttributes ; area: HTMLElementTagGlobalAttributes & { accesskey?: string ; alt?: string ; coords?: string ; download?: string ; href?: string ; hreflang?: string ; ping?: string ; rel?: string ; shape?: string ; target?: string ; type?: string } ; article: HTMLElementTagGlobalAttributes ; aside: HTMLElementTagGlobalAttributes ; audio: HTMLElementTagGlobalAttributes & { autoplay?: string ; controls?: string ; crossorigin?: string ; loop?: string ; mediagroup?: string ; muted?: string ; preload?: string ; src?: string } ; b: HTMLElementTagGlobalAttributes ; base: HTMLElementTagGlobalAttributes & { href?: string ; target?: string } ; bdi: HTMLElementTagGlobalAttributes ; bdo: HTMLElementTagGlobalAttributes & { dir?: string } ; blockquote: HTMLElementTagGlobalAttributes & { cite?: string } ; body: HTMLElementTagGlobalAttributes & { alink?: string ; background?: string ; bgcolor?: string ; bottommargin?: string ; leftmargin?: string ; link?: string ; onafterprint?: string ; onbeforeprint?: string ; onbeforeunload?: string ; onblur?: string ; onerror?: string ; onfocus?: string ; onhashchange?: string ; onlanguagechange?: string ; onload?: string ; onmessage?: string ; onoffline?: string ; ononline?: string ; onpagehide?: string ; onpageshow?: string ; onpopstate?: string ; onredo?: string ; onresize?: string ; onstorage?: string ; onundo?: string ; onunload?: string ; rightmargin?: string ; text?: string ; topmargin?: string ; vlink?: string } ; br: HTMLElementTagGlobalAttributes & { clear?: string } ; button: HTMLElementTagGlobalAttributes & { autocomplete?: string ; autofocus?: string ; disabled?: string ; form?: string ; formaction?: string ; formenctype?: string ; formmethod?: string ; formnovalidate?: string ; formtarget?: string ; name?: string ; type?: string ; value?: string } ; canvas: HTMLElementTagGlobalAttributes & { height?: string ; moz-opaque?: string ; width?: string } ; caption: HTMLElementTagGlobalAttributes & { align?: string } ; cite: HTMLElementTagGlobalAttributes ; code: HTMLElementTagGlobalAttributes ; col: HTMLElementTagGlobalAttributes & { align?: string ; span?: string } ; colgroup: HTMLElementTagGlobalAttributes & { align?: string ; span?: string } ; data: HTMLElementTagGlobalAttributes & { value?: string } ; datalist: HTMLElementTagGlobalAttributes ; dd: HTMLElementTagGlobalAttributes & { nowrap?: string } ; del: HTMLElementTagGlobalAttributes & { cite?: string ; datetime?: string } ; details: HTMLElementTagGlobalAttributes & { open?: string } ; dfn: HTMLElementTagGlobalAttributes ; dialog: HTMLElementTagGlobalAttributes & { open?: string } ; div: HTMLElementTagGlobalAttributes ; dl: HTMLElementTagGlobalAttributes ; dt: HTMLElementTagGlobalAttributes ; em: HTMLElementTagGlobalAttributes ; embed: HTMLElementTagGlobalAttributes & { height?: string ; src?: string ; type?: string ; width?: string } ; fieldset: HTMLElementTagGlobalAttributes & { disabled?: string ; form?: string ; name?: string } ; figcaption: HTMLElementTagGlobalAttributes ; figure: HTMLElementTagGlobalAttributes ; footer: HTMLElementTagGlobalAttributes ; form: HTMLElementTagGlobalAttributes & { accept?: string ; accept-charset?: string ; action?: string ; autocapitalize?: string ; autocomplete?: string ; enctype?: string ; method?: string ; name?: string ; novalidate?: string ; target?: string } ; h1: HTMLElementTagGlobalAttributes ; h2: HTMLElementTagGlobalAttributes ; h3: HTMLElementTagGlobalAttributes ; h4: HTMLElementTagGlobalAttributes ; h5: HTMLElementTagGlobalAttributes ; h6: HTMLElementTagGlobalAttributes ; head: HTMLElementTagGlobalAttributes & { profile?: string } ; header: HTMLElementTagGlobalAttributes ; hgroup: HTMLElementTagGlobalAttributes ; hr: HTMLElementTagGlobalAttributes & { align?: string ; color?: string ; noshade?: string ; size?: string ; width?: string } ; html: HTMLElementTagGlobalAttributes & { manifest?: string ; version?: string ; xmlns?: string } ; i: HTMLElementTagGlobalAttributes ; iframe: HTMLElementTagGlobalAttributes & { allow?: string ; allowfullscreen?: string ; allowpaymentrequest?: string ; csp?: string ; height?: string ; importance?: string ; name?: string ; referrerpolicy?: string ; sandbox?: string ; seamless?: string ; src?: string ; srcdoc?: string ; width?: string } ; img: HTMLElementTagGlobalAttributes & { alt?: string ; crossorigin?: string ; decoding?: string ; height?: string ; importance?: string ; intrinsicsize?: string ; ismap?: string ; loading?: string ; referrerpolicy?: string ; sizes?: string ; src?: string ; srcset?: string ; usemap?: string ; width?: string } ; input: HTMLElementTagGlobalAttributes & { accept?: string ; alt?: string ; autocomplete?: string ; autofocus?: string ; checked?: string ; dirname?: string ; disabled?: string ; form?: string ; formaction?: string ; formenctype?: string ; formmethod?: string ; formnovalidate?: string ; formtarget?: string ; height?: string ; inputmode?: string ; list?: string ; max?: string ; maxlength?: string ; min?: string ; minlength?: string ; multiple?: string ; name?: string ; pattern?: string ; placeholder?: string ; readonly?: string ; required?: string ; size?: string ; src?: string ; step?: string ; type?: string ; value?: string ; width?: string } ; ins: HTMLElementTagGlobalAttributes & { cite?: string ; datetime?: string } ; kbd: HTMLElementTagGlobalAttributes ; label: HTMLElementTagGlobalAttributes & { for?: string ; form?: string } ; legend: HTMLElementTagGlobalAttributes ; li: HTMLElementTagGlobalAttributes & { type?: string ; value?: string } ; link: HTMLElementTagGlobalAttributes & { as?: string ; crossorigin?: string ; href?: string ; hreflang?: string ; importance?: string ; integrity?: string ; media?: string ; referrerpolicy?: string ; rel?: string ; sizes?: string ; title?: string ; type?: string } ; main: HTMLElementTagGlobalAttributes ; map: HTMLElementTagGlobalAttributes & { name?: string } ; mark: HTMLElementTagGlobalAttributes ; menu: HTMLElementTagGlobalAttributes ; meta: HTMLElementTagGlobalAttributes & { charset?: string ; content?: string ; http-equiv?: string ; name?: string ; scheme?: string } ; meter: HTMLElementTagGlobalAttributes & { form?: string ; high?: string ; low?: string ; max?: string ; min?: string ; optimum?: string ; value?: string } ; nav: HTMLElementTagGlobalAttributes ; noscript: HTMLElementTagGlobalAttributes ; object: HTMLElementTagGlobalAttributes & { archive?: string ; border?: string ; classid?: string ; codebase?: string ; codetype?: string ; data?: string ; declare?: string ; form?: string ; height?: string ; name?: string ; standby?: string ; tabindex?: string ; type?: string ; typemustmatch?: string ; usemap?: string ; width?: string } ; ol: HTMLElementTagGlobalAttributes & { compact?: string ; reversed?: string ; start?: string ; type?: string } ; optgroup: HTMLElementTagGlobalAttributes & { disabled?: string ; label?: string } ; option: HTMLElementTagGlobalAttributes & { disabled?: string ; label?: string ; selected?: string ; value?: string } ; output: HTMLElementTagGlobalAttributes & { for?: string ; form?: string ; name?: string } ; p: HTMLElementTagGlobalAttributes ; param: HTMLElementTagGlobalAttributes & { name?: string ; type?: string ; value?: string ; valuetype?: string } ; picture: HTMLElementTagGlobalAttributes ; pre: HTMLElementTagGlobalAttributes & { cols?: string ; width?: string ; wrap?: string } ; progress: HTMLElementTagGlobalAttributes & { max?: string ; value?: string } ; q: HTMLElementTagGlobalAttributes & { cite?: string } ; rb: HTMLElementTagGlobalAttributes ; rp: HTMLElementTagGlobalAttributes ; rt: HTMLElementTagGlobalAttributes ; ruby: HTMLElementTagGlobalAttributes ; s: HTMLElementTagGlobalAttributes ; samp: HTMLElementTagGlobalAttributes ; script: HTMLElementTagGlobalAttributes & { async?: string ; charset?: string ; crossorigin?: string ; defer?: string ; integrity?: string ; nomodule?: string ; nonce?: string ; referrerpolicy?: string ; src?: string ; text?: string ; type?: string } ; section: HTMLElementTagGlobalAttributes ; select: HTMLElementTagGlobalAttributes & { autocomplete?: string ; autofocus?: string ; disabled?: string ; form?: string ; multiple?: string ; name?: string ; required?: string ; size?: string } ; slot: HTMLElementTagGlobalAttributes & { name?: string } ; small: HTMLElementTagGlobalAttributes ; source: HTMLElementTagGlobalAttributes & { media?: string ; sizes?: string ; src?: string ; srcset?: string ; type?: string } ; span: HTMLElementTagGlobalAttributes ; strong: HTMLElementTagGlobalAttributes ; style: HTMLElementTagGlobalAttributes & { media?: string ; nonce?: string ; scoped?: string ; title?: string ; type?: string } ; sub: HTMLElementTagGlobalAttributes ; summary: HTMLElementTagGlobalAttributes ; sup: HTMLElementTagGlobalAttributes ; table: HTMLElementTagGlobalAttributes & { align?: string ; border?: string } ; tbody: HTMLElementTagGlobalAttributes & { align?: string } ; td: HTMLElementTagGlobalAttributes & { abbr?: string ; align?: string ; axis?: string ; bgcolor?: string ; colspan?: string ; headers?: string ; rowspan?: string } ; template: HTMLElementTagGlobalAttributes ; textarea: HTMLElementTagGlobalAttributes & { autocapitalize?: string ; autocomplete?: string ; autofocus?: string ; cols?: string ; dirname?: string ; disabled?: string ; form?: string ; inputmode?: string ; maxlength?: string ; minlength?: string ; name?: string ; placeholder?: string ; readonly?: string ; required?: string ; rows?: string ; spellcheck?: string ; wrap?: string } ; tfoot: HTMLElementTagGlobalAttributes & { align?: string } ; th: HTMLElementTagGlobalAttributes & { abbr?: string ; align?: string ; axis?: string ; bgcolor?: string ; colspan?: string ; headers?: string ; rowspan?: string ; scope?: string ; sorted?: string } ; thead: HTMLElementTagGlobalAttributes & { align?: string } ; time: HTMLElementTagGlobalAttributes & { datetime?: string } ; title: HTMLElementTagGlobalAttributes ; tr: HTMLElementTagGlobalAttributes & { align?: string } ; track: HTMLElementTagGlobalAttributes & { default?: string ; kind?: string ; label?: string ; src?: string ; srclang?: string } ; u: HTMLElementTagGlobalAttributes ; ul: HTMLElementTagGlobalAttributes & { compact?: string } ; var: HTMLElementTagGlobalAttributes ; video: HTMLElementTagGlobalAttributes & { autoplay?: string ; controls?: string ; crossorigin?: string ; height?: string ; loop?: string ; mediagroup?: string ; muted?: string ; poster?: string ; preload?: string ; src?: string ; width?: string } ; wbr: HTMLElementTagGlobalAttributes }

Map of HTML element tag attributes.

Remarks

If you need the type of the HTML attributes of an HTML element, this is it.

Example

1
const getAttribute =
2
	<Tag extends keyof HTMLElementTagAttributeMap>(tag: Tag) =>
3
	(attribute: keyof HTMLElementTagAttributeMap[Tag]) => // …

See

HTMLElementTagGlobalAttributes
ReadOnlyRecord

HTMLElementTagGlobalAttributes

Ƭ HTMLElementTagGlobalAttributes: Object

Global HTML attributes.

Remarks

If you need the type of all HTML attributes, this is it.

Example

1
const getAttribute = (attribute: keyof HTMLElementTagGlobalAttributes) => // …

See

ReadOnlyRecord

Type declaration

Name	Type	Description
`accesskey (optional)`	`string`	Provides a hint for generating a keyboard shortcut for the current element. This attribute consists of a space-separated list of characters. The browser should use the first one that exists on the computer keyboard layout. --- References `See` MDN Reference
`aria-activedescendant (optional)`	`string`	Identifies the currently active element when DOM focus is on a `composite` widget, `textbox`, `group`, or `application`. --- References `See` WAI-ARIA Reference
`aria-atomic (optional)`	`string`	Indicates whether assistive technologies will present all, or only parts of, the changed region based on the change notifications defined by the `aria-relevant` attribute. --- References `See` WAI-ARIA Reference
`aria-autocomplete (optional)`	`string`	Indicates whether inputting text could trigger display of one or more predictions of the user’s intended value for an input and specifies how predictions would be presented if they are made. --- References `See` WAI-ARIA Reference
`aria-busy (optional)`	`string`	Indicates an element is being modified and that assistive technologies MAY want to wait until the modifications are complete before exposing them to the user. --- References `See` WAI-ARIA Reference
`aria-checked (optional)`	`string`	Indicates the current “checked” state of checkboxes, radio buttons, and other widgets. See related `aria-pressed` and `aria-selected`. --- References `See` WAI-ARIA Reference
`aria-colcount (optional)`	`string`	Defines the total number of columns in a `table`, `grid`, or `treegrid`. See related `aria-colindex`. --- References `See` WAI-ARIA Reference
`aria-colindex (optional)`	`string`	Defines an element’s column index or position with respect to the total number of columns within a `table`, `grid`, or `treegrid`. See related `aria-colcount` and `aria-colspan`. --- References `See` WAI-ARIA Reference
`aria-colspan (optional)`	`string`	Defines the number of columns spanned by a cell or gridcell within a `table`, `grid`, or `treegrid`. See related `aria-colindex` and `aria-rowspan`. --- References `See` WAI-ARIA Reference
`aria-controls (optional)`	`string`	Identifies the element (or elements) whose contents or presence are controlled by the current element. See related `aria-owns`. --- References `See` WAI-ARIA Reference
`aria-current (optional)`	`string`	Indicates the element that represents the current item within a container or set of related elements. --- References `See` WAI-ARIA Reference
`aria-describedby (optional)`	`string`	Identifies the element (or elements) that describes the object. See related `aria-labelledby`. --- References `See` WAI-ARIA Reference
`aria-details (optional)`	`string`	Identifies the element that provides a detailed, extended description for the object. See related `aria-describedby`.
`aria-disabled (optional)`	`string`	Indicates that the element is perceivable but disabled, so it is not editable or otherwise operable. See related `aria-hidden` and `aria-readonly`. --- References `See` WAI-ARIA Reference
`aria-dropeffect (optional)`	`string`	[Deprecated in ARIA 1.1] Indicates what functions can be performed when a dragged object is released on the drop target. --- References `See` WAI-ARIA Reference
`aria-errormessage (optional)`	`string`	Identifies the element that provides an error message for the object. See related `aria-invalid` and `aria-describedby`. --- References `See` WAI-ARIA Reference
`aria-expanded (optional)`	`string`	Indicates whether the element, or another grouping element it controls, is currently expanded or collapsed. --- References `See` WAI-ARIA Reference
`aria-flowto (optional)`	`string`	Identifies the next element (or elements) in an alternate reading order of content which, at the user’s discretion, allows assistive technology to override the general default of reading in document source order. --- References `See` WAI-ARIA Reference
`aria-grabbed (optional)`	`string`	[Deprecated in ARIA 1.1] Indicates an element’s “grabbed” state in a drag-and-drop operation. --- References `See` WAI-ARIA Reference
`aria-haspopup (optional)`	`string`	Indicates the availability and type of interactive popup element, such as menu or dialog, that can be triggered by an element. --- References `See` WAI-ARIA Reference
`aria-hidden (optional)`	`string`	Indicates whether the element is exposed to an accessibility API. See related `aria-disabled`. --- References `See` WAI-ARIA Reference
`aria-invalid (optional)`	`string`	Indicates the entered value does not conform to the format expected by the application. See related `aria-errormessage`. --- References `See` WAI-ARIA Reference
`aria-keyshortcuts (optional)`	`string`	Indicates keyboard shortcuts that an author has implemented to activate or give focus to an element.
`aria-label (optional)`	`string`	Defines a string value that labels the current element. See related `aria-labelledby`. --- References `See` WAI-ARIA Reference
`aria-labelledby (optional)`	`string`	Identifies the element (or elements) that labels the current element. See related `aria-describedby`. --- References `See` WAI-ARIA Reference
`aria-level (optional)`	`string`	Defines the hierarchical level of an element within a structure. --- References `See` WAI-ARIA Reference
`aria-live (optional)`	`string`	Indicates that an element will be updated, and describes the types of updates the user agents, assistive technologies, and user can expect from the live region. --- References `See` WAI-ARIA Reference
`aria-modal (optional)`	`string`	Indicates whether an element is modal when displayed. --- References `See` WAI-ARIA Reference
`aria-multiline (optional)`	`string`	Indicates whether a text box accepts multiple lines of input or only a single line. --- References `See` WAI-ARIA Reference
`aria-multiselectable (optional)`	`string`	Indicates that the user may select more than one item from the current selectable descendants. --- References `See` WAI-ARIA Reference
`aria-orientation (optional)`	`string`	Indicates whether the element’s orientation is horizontal, vertical, or unknown/ambiguous. --- References `See` WAI-ARIA Reference
`aria-owns (optional)`	`string`	Identifies an element (or elements) in order to define a visual, functional, or contextual parent/child relationship between DOM elements where the DOM hierarchy cannot be used to represent the relationship. See related `aria-controls`. --- References `See` WAI-ARIA Reference
`aria-placeholder (optional)`	`string`	Defines a short hint (a word or short phrase) intended to aid the user with data entry when the control has no value. A hint could be a sample value or a brief description of the expected format. --- References `See` WAI-ARIA Reference
`aria-posinset (optional)`	`string`	Defines an element’s number or position in the current set of listitems or treeitems. Not required if all elements in the set are present in the DOM. See related `aria-setsize`. --- References `See` WAI-ARIA Reference
`aria-pressed (optional)`	`string`	Indicates the current “pressed” state of toggle buttons. See related `aria-checked` and `aria-selected`. --- References `See` WAI-ARIA Reference
`aria-readonly (optional)`	`string`	Indicates that the element is not editable, but is otherwise operable. See related `aria-disabled`. --- References `See` WAI-ARIA Reference
`aria-relevant (optional)`	`string`	Indicates what notifications the user agent will trigger when the accessibility tree within a live region is modified. See related `aria-atomic`. --- References `See` WAI-ARIA Reference
`aria-required (optional)`	`string`	Indicates that user input is required on the element before a form may be submitted. --- References `See` WAI-ARIA Reference
`aria-roledescription (optional)`	`string`	Defines a human-readable, author-localized description for the role of an element. --- References `See` WAI-ARIA Reference
`aria-rowcount (optional)`	`string`	Defines the total number of rows in a `table`, `grid`, or `treegrid`. See related `aria-rowindex`. --- References `See` WAI-ARIA Reference
`aria-rowindex (optional)`	`string`	Defines an element’s row index or position with respect to the total number of rows within a `table`, `grid`, or `treegrid`. See related `aria-rowcount` and `aria-rowspan`. --- References `See` WAI-ARIA Reference
`aria-rowspan (optional)`	`string`	Defines the number of rows spanned by a cell or gridcell within a `table`, `grid`, or `treegrid`. See related `aria-rowindex` and `aria-colspan`. --- References `See` WAI-ARIA Reference
`aria-selected (optional)`	`string`	Indicates the current “selected” state of various widgets. See related `aria-checked` and `aria-pressed`. --- References `See` WAI-ARIA Reference
`aria-setsize (optional)`	`string`	Defines the number of items in the current set of listitems or treeitems. Not required if all elements in the set are present in the DOM. See related `aria-posinset`. --- References `See` WAI-ARIA Reference
`aria-sort (optional)`	`string`	Indicates if items in a table or grid are sorted in ascending or descending order. --- References `See` WAI-ARIA Reference
`aria-valuemax (optional)`	`string`	Defines the maximum allowed value for a range widget. --- References `See` WAI-ARIA Reference
`aria-valuemin (optional)`	`string`	Defines the minimum allowed value for a range widget. --- References `See` WAI-ARIA Reference
`aria-valuenow (optional)`	`string`	Defines the current value for a range widget. See related `aria-valuetext`. --- References `See` WAI-ARIA Reference
`aria-valuetext (optional)`	`string`	Defines the human readable text alternative of `aria-valuenow` for a range widget. --- References `See` WAI-ARIA Reference
`autocapitalize (optional)`	`string`	Controls whether and how text input is automatically capitalized as it is entered/edited by the user. It can have the following values: _ `off` or `none`, no autocapitalization is applied (all letters default to lowercase) _ `on` or `sentences`, the first letter of each sentence defaults to a capital letter; all other letters default to lowercase _ `words`, the first letter of each word defaults to a capital letter; all other letters default to lowercase _ `characters`, all letters should default to uppercase --- References `See` MDN Reference
`class (optional)`	`string`	A space-separated list of the classes of the element. Classes allows CSS and JavaScript to select and access specific elements via the class selectors or functions like the method `Document.getElementsByClassName()`. --- References `See` MDN Reference
`contenteditable (optional)`	`string`	An enumerated attribute indicating if the element should be editable by the user. If so, the browser modifies its widget to allow editing. The attribute must take one of the following values: _ `true` or the empty string, which indicates that the element must be editable; _ `false`, which indicates that the element must not be editable. --- References `See` MDN Reference
`contextmenu (optional)`	`string`	The `[id](#attr-id)` of a `<menu>` to use as the contextual menu for this element. --- References `See` MDN Reference
`dir (optional)`	`string`	An enumerated attribute indicating the directionality of the element’s text. It can have the following values: _ `ltr`, which means left to right and is to be used for languages that are written from the left to the right (like English); _ `rtl`, which means right to left and is to be used for languages that are written from the right to the left (like Arabic); * `auto`, which lets the user agent decide. It uses a basic algorithm as it parses the characters inside the element until it finds a character with a strong directionality, then it applies that directionality to the whole element. --- References `See` MDN Reference
`draggable (optional)`	`string`	An enumerated attribute indicating whether the element can be dragged, using the Drag and Drop API. It can have the following values: _ `true`, which indicates that the element may be dragged _ `false`, which indicates that the element may not be dragged. --- References `See` MDN Reference
`dropzone (optional)`	`string`	An enumerated attribute indicating what types of content can be dropped on an element, using the Drag and Drop API. It can have the following values: _ `copy`, which indicates that dropping will create a copy of the element that was dragged _ `move`, which indicates that the element that was dragged will be moved to this new location. * `link`, will create a link to the dragged data.
`exportparts (optional)`	`string`	Used to transitively export shadow parts from a nested shadow tree into a containing light tree. --- References `See` MDN Reference
`hidden (optional)`	`string`	A Boolean attribute indicates that the element is not yet, or is no longer, relevant. For example, it can be used to hide elements of the page that can’t be used until the login process has been completed. The browser won’t render such elements. This attribute must not be used to hide content that could legitimately be shown. --- References `See` MDN Reference
`id (optional)`	`string`	Defines a unique identifier (ID) which must be unique in the whole document. Its purpose is to identify the element when linking (using a fragment identifier), scripting, or styling (with CSS). --- References `See` MDN Reference
`inputmode (optional)`	`string`	Provides a hint to browsers as to the type of virtual keyboard configuration to use when editing this element or its contents. Used primarily on `<input>` elements, but is usable on any element while in `[contenteditable](https://developer.mozilla.org/docs/Web/HTML/Global_attributes#attr-contenteditable)` mode. --- References `See` MDN Reference
`is (optional)`	`string`	Allows you to specify that a standard HTML element should behave like a registered custom built-in element (see Using custom elements for more details). --- References `See` MDN Reference
`itemid (optional)`	`string`	The unique, global identifier of an item. --- References `See` MDN Reference
`itemprop (optional)`	`string`	Used to add properties to an item. Every HTML element may have an `itemprop` attribute specified, where an `itemprop` consists of a name and value pair. --- References `See` MDN Reference
`itemref (optional)`	`string`	Properties that are not descendants of an element with the `itemscope` attribute can be associated with the item using an `itemref`. It provides a list of element ids (not `itemid`s) with additional properties elsewhere in the document. --- References `See` MDN Reference
`itemscope (optional)`	`string`	`itemscope` (usually) works along with `[itemtype](https://developer.mozilla.org/docs/Web/HTML/Global_attributes#attr-itemtype)` to specify that the HTML contained in a block is about a particular item. `itemscope` creates the Item and defines the scope of the `itemtype` associated with it. `itemtype` is a valid URL of a vocabulary (such as schema.org) that describes the item and its properties context. --- References `See` MDN Reference
`itemtype (optional)`	`string`	Specifies the URL of the vocabulary that will be used to define `itemprop`s (item properties) in the data structure. `[itemscope](https://developer.mozilla.org/docs/Web/HTML/Global_attributes#attr-itemscope)` is used to set the scope of where in the data structure the vocabulary set by `itemtype` will be active. --- References `See` MDN Reference
`lang (optional)`	`string`	Helps define the language of an element: the language that non-editable elements are in, or the language that editable elements should be written in by the user. The attribute contains one “language tag” (made of hyphen-separated “language subtags”) in the format defined in Tags for Identifying Languages (BCP47). xml:lang has priority over it. --- References `See` MDN Reference
`onabort (optional)`	`string`	The loading of a resource has been aborted.
`onblur (optional)`	`string`	An element has lost focus (does not bubble).
`oncanplay (optional)`	`string`	The user agent can play the media, but estimates that not enough data has been loaded to play the media up to its end without having to stop for further buffering of content.
`oncanplaythrough (optional)`	`string`	The user agent can play the media up to its end without having to stop for further buffering of content.
`onchange (optional)`	`string`	The change event is fired for , elements when a change to the element’s value is committed by the user.
`onclick (optional)`	`string`	A pointing device button has been pressed and released on an element.
`oncontextmenu (optional)`	`string`	The right button of the mouse is clicked (before the context menu is displayed).
`ondblclick (optional)`	`string`	A pointing device button is clicked twice on an element.
`ondrag (optional)`	`string`	An element or text selection is being dragged (every 350ms).
`ondragend (optional)`	`string`	A drag operation is being ended (by releasing a mouse button or hitting the escape key).
`ondragenter (optional)`	`string`	A dragged element or text selection enters a valid drop target.
`ondragleave (optional)`	`string`	A dragged element or text selection leaves a valid drop target.
`ondragover (optional)`	`string`	An element or text selection is being dragged over a valid drop target (every 350ms).
`ondragstart (optional)`	`string`	The user starts dragging an element or text selection.
`ondrop (optional)`	`string`	An element is dropped on a valid drop target.
`ondurationchange (optional)`	`string`	The duration attribute has been updated.
`onemptied (optional)`	`string`	The media has become empty; for example, this event is sent if the media has already been loaded (or partially loaded), and the load() method is called to reload it.
`onended (optional)`	`string`	Playback has stopped because the end of the media was reached.
`onerror (optional)`	`string`	A resource failed to load.
`onfocus (optional)`	`string`	An element has received focus (does not bubble).
`onformchange (optional)`	`string`	-
`onforminput (optional)`	`string`	-
`oninput (optional)`	`string`	The value of an element changes or the content of an element with the attribute contenteditable is modified.
`oninvalid (optional)`	`string`	A submittable element has been checked and doesn’t satisfy its constraints.
`onkeydown (optional)`	`string`	A key is pressed down.
`onkeypress (optional)`	`string`	A key is pressed down and that key normally produces a character value (use input instead).
`onkeyup (optional)`	`string`	A key is released.
`onload (optional)`	`string`	A resource and its dependent resources have finished loading.
`onloadeddata (optional)`	`string`	The first frame of the media has finished loading.
`onloadedmetadata (optional)`	`string`	The metadata has been loaded.
`onloadstart (optional)`	`string`	Progress has begun.
`onmousedown (optional)`	`string`	A pointing device button (usually a mouse) is pressed on an element.
`onmouseenter (optional)`	`string`	A pointing device is moved onto the element that has the listener attached.
`onmouseleave (optional)`	`string`	A pointing device is moved off the element that has the listener attached.
`onmousemove (optional)`	`string`	A pointing device is moved over an element.
`onmouseout (optional)`	`string`	A pointing device is moved off the element that has the listener attached or off one of its children.
`onmouseover (optional)`	`string`	A pointing device is moved onto the element that has the listener attached or onto one of its children.
`onmouseup (optional)`	`string`	A pointing device button is released over an element.
`onmousewheel (optional)`	`string`	-
`onpause (optional)`	`string`	Playback has been paused.
`onplay (optional)`	`string`	Playback has begun.
`onplaying (optional)`	`string`	Playback is ready to start after having been paused or delayed due to lack of data.
`onpointercancel (optional)`	`string`	The pointer is unlikely to produce any more events.
`onpointerdown (optional)`	`string`	The pointer enters the active buttons state.
`onpointerenter (optional)`	`string`	Pointing device is moved inside the hit-testing boundary.
`onpointerleave (optional)`	`string`	Pointing device is moved out of the hit-testing boundary.
`onpointerlockchange (optional)`	`string`	The pointer was locked or released.
`onpointerlockerror (optional)`	`string`	It was impossible to lock the pointer for technical reasons or because the permission was denied.
`onpointermove (optional)`	`string`	The pointer changed coordinates.
`onpointerout (optional)`	`string`	The pointing device moved out of hit-testing boundary or leaves detectable hover range.
`onpointerover (optional)`	`string`	The pointing device is moved into the hit-testing boundary.
`onpointerup (optional)`	`string`	The pointer leaves the active buttons state.
`onprogress (optional)`	`string`	In progress.
`onratechange (optional)`	`string`	The playback rate has changed.
`onreadystatechange (optional)`	`string`	The readyState attribute of a document has changed.
`onreset (optional)`	`string`	A form is reset.
`onresize (optional)`	`string`	The document view has been resized.
`onscroll (optional)`	`string`	The document view or an element has been scrolled.
`onseeked (optional)`	`string`	A seek operation completed.
`onseeking (optional)`	`string`	A seek operation began.
`onselect (optional)`	`string`	Some text is being selected.
`onshow (optional)`	`string`	A contextmenu event was fired on/bubbled to an element that has a contextmenu attribute
`onstalled (optional)`	`string`	The user agent is trying to fetch media data, but data is unexpectedly not forthcoming.
`onsubmit (optional)`	`string`	A form is submitted.
`onsuspend (optional)`	`string`	Media data loading has been suspended.
`ontimeupdate (optional)`	`string`	The time indicated by the currentTime attribute has been updated.
`onvolumechange (optional)`	`string`	The volume has changed.
`onwaiting (optional)`	`string`	Playback has stopped because of a temporary lack of data.
`part (optional)`	`string`	A space-separated list of the part names of the element. Part names allows CSS to select and style specific elements in a shadow tree via the `::part` pseudo-element. --- References `See` MDN Reference
`role (optional)`	`string`	-
`slot (optional)`	`string`	Assigns a slot in a shadow DOM shadow tree to an element: An element with a `slot` attribute is assigned to the slot created by the `<slot>` element whose `[name](https://developer.mozilla.org/docs/Web/HTML/Element/slot#attr-name)` attribute’s value matches that `slot` attribute’s value. --- References `See` MDN Reference
`spellcheck (optional)`	`string`	An enumerated attribute defines whether the element may be checked for spelling errors. It may have the following values: _ `true`, which indicates that the element should be, if possible, checked for spelling errors; _ `false`, which indicates that the element should not be checked for spelling errors. --- References `See` MDN Reference
`style (optional)`	`string`	Contains CSS styling declarations to be applied to the element. Note that it is recommended for styles to be defined in a separate file or files. This attribute and the `<style>` element have mainly the purpose of allowing for quick styling, for example for testing purposes. --- References `See` MDN Reference
`tabindex (optional)`	`string`	An integer attribute indicating if the element can take input focus (is focusable), if it should participate to sequential keyboard navigation, and if so, at what position. It can take several values: _ a negative value means that the element should be focusable, but should not be reachable via sequential keyboard navigation; _ `0` means that the element should be focusable and reachable via sequential keyboard navigation, but its relative order is defined by the platform convention; * a positive value means that the element should be focusable and reachable via sequential keyboard navigation; the order in which the elements are focused is the increasing value of the tabindex. If several elements share the same tabindex, their relative order follows their relative positions in the document. --- References `See` MDN Reference
`title (optional)`	`string`	Contains a text representing advisory information related to the element it belongs to. Such information can typically, but not necessarily, be presented to the user as a tooltip. --- References `See` MDN Reference
`translate (optional)`	`string`	An enumerated attribute that is used to specify whether an element’s attribute values and the values of its `Text` node children are to be translated when the page is localized, or whether to leave them unchanged. It can have the following values: _ empty string and `yes`, which indicates that the element will be translated. _ `no`, which indicates that the element will not be translated. --- References `See` MDN Reference

Iterables

IsomorphicIterable

Ƭ IsomorphicIterable<Item>: Readonly<AsyncIterable<Item> | Iterable<Item>>

Value might be an AsyncIterable or just an Iterable (read-only).

Remarks

Union type useful when you want to accept both AsyncIterable and Iterable values, which is generally in asynchronous functions that can loop over @@asyncIterator or @@iterator values.

Example

1
const iterable: IsomorphicIterable<number> = [1, 2, 3];
2

3
for (const item of iterable) {
4
	console.log(item); // Works
5
}
6

7
for await (const item of iterable) {
8
	console.log(item); // Also works
9
}

See

Type parameters

Name	Type	Description
`Item`	`unknown`	Type of the items in the iterable.

IsomorphicIterableItem

Ƭ IsomorphicIterableItem<SourceIterable>: SourceIterable extends IsomorphicIterable<infer Item> ? Item : never

Type of the items of an IsomorphicIterable.

Remarks

Sometimes we have to get the item type out of an IsomorphicIterable. This type is meant to be used where inference is not an option.

Example

1
const iterable: IsomorphicIterable<number> = [1, 2, 3];
2
const item: IsomorphicIterableItem<typeof iterable> = 1;

See

IsomorphicIterable

Type parameters

Name	Type	Description
`SourceIterable`	extends `IsomorphicIterable`	`IsomorphicIterable` type to get the item type from.`

IsomorphicIterableIterator

Ƭ IsomorphicIterableIterator<Item>: Readonly<AsyncIterableIterator<Item> | IterableIterator<Item>>

Value might be an AsyncIterableIterator or just an IterableIterator (read-only).

Remarks

This is just an read-only alternative to AsyncIterableIterator or IterableIterator to avoid unwanted mutations.

Example

1
const iterable: IsomorphicIterableIterator<number> = [1, 2, 3];

Type parameters

Name	Type	Description
`Item`	`unknown`	Type of the items in the `AsyncIterableIterator` or `IterableIterator`.

IsomorphicIterator

Ƭ IsomorphicIterator<Item, Return, Next>: Readonly<AsyncIterator<Item, Return, Next> | Iterator<Item, Return, Next>>

Value might be an AsyncIterator or just an Iterator (read-only).

Remarks

This is just an read-only alternative to AsyncIterator or Iterator to avoid unwanted mutations.

Example

1
const iterator: IsomorphicIterator<number> = [1, 2, 3];

Type parameters

Name	Type	Description
`Item`	`unknown`	Type of the items in the `AsyncIterator` or `Iterator`.
`Return`	`void`	Type of the return value in the `AsyncIterator` or `Iterator`.
`Next`	`void`	Type of the next value in the `AsyncIterator` or `Iterator`.

ReadOnlyIterable

Ƭ ReadOnlyIterable<Item>: Readonly<Iterable<Item>>

Read-only Iterable.

Remarks

This is just an read-only alternative to Iterable to avoid unwanted mutations.

Example

1
const test1: ReadOnlyIterable<number> = [1, 2, 3]; // ok
2
const test2: ReadOnlyIterable<string> = [1, 2, 3]; // error

Type parameters

Name	Type	Description
`Item`	`unknown`	Type of the items in the `Iterable`.

ReadOnlyIterableIterator

Ƭ ReadOnlyIterableIterator<Item>: Readonly<IterableIterator<Item>>

Read-only IterableIterator.

Remarks

This is just an read-only alternative to IterableIterator to avoid unwanted mutations.

Type parameters

Name	Type	Description
`Item`	`unknown`	Type of the items in the `IterableIterator`.

ReadOnlyIterator

Ƭ ReadOnlyIterator<Item, Return, Next>: Readonly<Iterator<Item, Return, Next>>

Read-only Iterator.

Remarks

This is just an read-only alternative to Iterator to avoid unwanted mutations.

Type parameters

Name	Type	Description
`Item`	`unknown`	Type of the items in the `Iterator`.
`Return`	`void`	Type of the return value in the `Iterator`.
`Next`	`void`	Type of the next value in the `Iterator`.

Number

Digit

Ƭ Digit: Enumerate<9>

Valid digits (0 to 9).

Remarks

The idea with this type is to use it to construct others based on it, like for example Digit2 for 00 to 99.

Example

1
const numbers: Iterable<Digit> = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

See

Enumerate

Enumerate

Ƭ Enumerate<To, Accumulator>: Accumulator["length"] extends To ? Accumulator[number] | To : Enumerate<To, […Accumulator, Accumulator["length"]]>

Union of numbers from 0 to To

Remarks

Recursively generates a type with an union of numbers from 0 to Length - 1. This has the same limit TypeScript has for recursive types.

Example

1
type From0To10 = Enumerate<10>;

Type parameters

Name	Type	Description
`To`	extends `number`	Last number of the union (starts at 0).
`Accumulator`	extends `ReadonlyArray`<`number`> = []	Accumulator for the recursion (for internal use).

MultiDigitNumberString

Ƭ MultiDigitNumberString: `${bigint}${bigint}`

String with more than 1 number on it.

Remarks

This type is useful when a given string will need more than one number on it.

Example

1
const test1: MultiDigitNumberString = "01"; // ok
2
const test2: MultiDigitNumberString = "1"; // error

Numeric

Ƭ Numeric: bigint | number

Types to represent numbers.

Remarks

The Numeric type is a union of number and bigint. It is useful for cases where a value could be either a regular JavaScript number or a BigInt.

Example

1
const numericNumber: Numeric = 42;
2
const numericBigInt: Numeric = 42n;

Radix

Ƭ Radix: Range<2, 36>

Valid radix values (from 2 to 36).

Remarks

The Radix type is useful when working with number bases other than decimal. The radix defines the base of the number system being used. For example, a binary system has a radix of 2, a decimal system has a radix of 10, and a hexadecimal system has a radix of 16. The Radix type can be used to ensure that a given radix value is within the valid range of 2 to 36.

Example

1
const binary: Radix = 2;
2
const decimal: Radix = 10;
3
const hexadecimal: Radix = 16;

See

Range

Range

Ƭ Range<From, To>: Exclude<Enumerate<To>, Enumerate<From>> | From

Generates a range of numbers using Enumerate with given Length and omitting the first From numbers.

Remarks

This type is equivalent to an array of numbers where the first From elements are excluded and the length of the array is Length - From. The idea is to use it to generate a range of numbers from the given From, and of the given Length.

Example

1
type From5To10 = Range<5, 10>; // 5, 6, 7, 8, 9, 10

See

Enumerate

Type parameters

Name	Type
`From`	extends `number`
`To`	extends `number`

Object

Empty

Ƭ Empty: EmptyArray | EmptyRecord | EmptyString

Empty array, object or string.

Remarks

Union type of EmptyArray, EmptyRecord and EmptyString, to signify values that are empty.

Example

1
const emptyString: Empty = "";
2
const emptyArray: Empty = [];
3
const emptyRecord: Empty = {};

See

EmptyArray
EmptyRecord
EmptyString

EmptyRecord

Ƭ EmptyRecord: ReadOnlyRecord<PropertyKey, never>

Empty record (object).

Remarks

This is a type alias for an empty readonly record. Accessing properties gives undefined.

Example

1
const emptyRecord: EmptyRecord = {};

See

ReadOnlyRecord

Entry

Ƭ Entry<Key, Value>: readonly [key: Key, value: Value]

Entry couple [key, value].

Remarks

It is a tuple of two elements, the first one being the key and the second one being the value of an object’s property.

Example

1
const entry: Entry<string, number> = ["🟢", 1];

Type parameters

Name	Type	Description
`Key`	`PropertyKey`	Object’s properties type.
`Value`	`unknown`	Object’s values type.

EntryKey

Ƭ EntryKey<Input>: Input[0]

Key of an Entry.

Remarks

Util type to get the key of an Entry.

Example

1
const entry: Entry<string, number> = ["🟢", 1];
2
const entryKey: EntryKey<typeof entry> = entry[0];

See

Entry

Type parameters

Name	Type	Description
`Input`	extends `Entry`	Entry type.

EntryOf

Ƭ EntryOf<Type>: Entry<KeyOf<Type>, ValueOf<Type>>

Object or array Entry.

Remarks

Get the Entry type out of an object or array.

Example

1
const object = {
2
	"🟢": 1,
3
	"🟩": 2,
4
};
5
const entries: EntryOf<typeof object> = Object.entries(object)[0];

See

Entry
KeyOf
ValueOf

Type parameters

Name	Type	Description
`Type`	extends `object`	Object or array type.

EntryValue

Ƭ EntryValue<Input>: Input[1]

Value of an Entry.

Remarks

Util type to get the value of an Entry.

Example

1
const entry: Entry<string, number> = ["🟢", 1];
2
const entryValue: EntryValue<typeof entry> = entry[1];

See

Entry

Type parameters

Name	Type	Description
`Input`	extends `Entry`	Entry type.

KeyOf

Ƭ KeyOf<Type>: Type extends ArrayLike ? NeverFallback<Just<Exclude<Partial<Type>["length"], Type["length"]>>, number> : `${Exclude<keyof Type, symbol>}`

Generic key for either object or array.

Remarks

Type to represent the type of the key in an array or object. It automatically omits symbol keys from objects, and uses number for arrays with dynamic length.

Example

1
const array = [1, 2, 3] as const;
2
const object = { "🟢": "🟩" } as const;
3

4
const arrayKey: KeyOf<typeof array> = 0;
5
const objectKey: KeyOf<typeof object> = "🟢";

Type parameters

Name	Type	Description
`Type`	extends `object`	Object or array type.

MaybeEmpty

Creates an union of the given type with a possible “empty” value.

Remarks

This type is useful to make clear that we expect a possible empty value.

Example

1
type Greet: MaybeEmpty<"Hello">; // "Hello" | ""
2
type Triple: MaybeEmpty<readonly [1, 2, 3]>; // readonly [1, 2, 3] | readonly []
3
type Foo: MaybeEmpty<{ readonly foo: "bar" }>; // { readonly foo: "bar" } | {}

See

Either
EmptyArray
EmptyRecord
EmptyString

Type parameters

Name	Description
`Input`	Type to unite with it’s empty counterpart.

NotEmpty

Ƭ NotEmpty<Type>: Exclude<Type, Empty>

Type for a non-empty ArrayLike, object or string.

Remarks

Example

1
const notEmptyString: NotEmpty<string> = "🟢";
2
const notEmptyArray: NotEmpty<ReadOnlyArray> = ["🟢", "🟩"];
3
const notEmptyRecord: NotEmpty<ReadOnlyRecord> = { "🟢": "🟩" };

See

Empty

Type parameters

Name	Type	Description
`Type`	extends `ArrayLike` \| `object` \| `string`	The type to check.

ReadOnlyRecord

Ƭ ReadOnlyRecord<Key, Value>: Readonly<Record<Key, Value>>

Read-only record.

Remarks

There’s already a native Readonly and Record type, but this type has default type parameters to make it easier to use when the type of a record is unknown.

Example

1
const record: ReadOnlyRecord<string, Array<number>> = {
2
	"🟢": [1, 2, 3],
3
	"🟩": [4, 5, 6],
4
};
5
record["🟢"][0] = 7; // Error

Type parameters

Name	Type	Description
`Key`	extends `PropertyKey` = `PropertyKey`	Type of the keys in the record.
`Value`	`unknown`	Type of the values in the record.

ValueOf

Ƭ ValueOf<Type>: KeyOf<Type> extends keyof Type ? Type[KeyOf<Type>] : never

Generic key for either object or array.

Remarks

This type is used to get the type of the values in a collection (items of an ArrayLike or properties of a Record).

Example

1
const object = {
2
	"🟢": 1,
3
	"🟩": 2,
4
};
5
const key: ValueOf<typeof object> = 1;

See

KeyOf

Type parameters

Name	Type	Description
`Type`	extends `object`	Object or array type.

RegExp

RegularExpression

Ƭ RegularExpression: `/${string}/${RegularExpressionFlags}`

String representing a regular expression.

Remarks

Safer than string and simpler than RegExp type to represent a regular expression. It RegularExpression to enforce flags to always have u and have a consistent order.

Example

1
const regex: RegularExpression = "/^[a-z]+$/u";

See

RegularExpressionFlags

Ƭ RegularExpressionFlags: `${MaybeEmpty<“g”>}${MaybeEmpty<“i”>}${MaybeEmpty<“m”>}${MaybeEmpty<“s”>}u`

Possible combinations of regular expression flags (with mandatory u flag).

Remarks

Type union stricter than string type for RegExp flags. The unicode flag is mandatory to ensure unicode characters are always supported.

Example

1
const flags1: RegularExpressionFlags = "u";
2
const flags2: RegularExpressionFlags = "gu";
3
const flags3: RegularExpressionFlags = "iu";
4
const flags4: RegularExpressionFlags = "giu";

See

Regular Expressions

String

Empty

Ƭ Empty: EmptyArray | EmptyRecord | EmptyString

Empty array, object or string.

Remarks

Union type of EmptyArray, EmptyRecord and EmptyString, to signify values that are empty.

Example

1
const emptyString: Empty = "";
2
const emptyArray: Empty = [];
3
const emptyRecord: Empty = {};

See

EmptyArray
EmptyRecord
EmptyString

EmptyString

Ƭ EmptyString: typeof EMPTY_STRING

Empty string.

Remarks

This type is a string with no characters on it (length 0). EmptyString.

Example

1
const emptyString: EmptyString = "";

Head

Ƭ Head<Input>: HeadAndTail<Input>[0]

Initial value of an ArrayLike.

Remarks

Given a type argument (an ArrayLike), this returns the type of the item in index 0.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const head: Head<typeof array> = "🟢";

See

ArrayLike
HeadAndTail

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	`ArrayLike` value (such as `Array` or `string`).

HeadAndTail

Get a couple with the head and tail types of an ArrayLike.

Remarks

Given a type argument (an ArrayLike), this returns a couple with the type of the item in index 0 first, and the rest of the ArrayLike after.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const headAndTail: HeadAndTail<typeof array> = ["🟢", ["🟩", "💚"]];

See

ArrayLike
EmptyArray
EmptyString
Head
Maybe
Tail

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	Input `ArrayLike`.

Initial

Ƭ Initial<Input>: InitialAndLast<Input>[0]

Initial values of an ArrayLike (omitting the last).

Remarks

Given a type argument (an ArrayLike), this returns the type of the items from the start of the ArrayLike until the before to last item.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const initial: Initial<typeof array> = ["🟢", "🟩"];

See

ArrayLike
InitialAndLast

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	`ArrayLike` value (such as `Array` or `string`).

InitialAndLast

Get a couple with the initial and last types of an ArrayLike.

Remarks

Given a ArrayLike, this returns a couple with the type of all items from the start until the item before last, and then the last.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const initialAndLast: InitialAndLast<typeof array> = [["🟢", "🟩"], "💚"];

See

ArrayLike
EmptyArray
EmptyString
Head
Initial
Last
Maybe

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	Input `ArrayLike`.

Last

Ƭ Last<Input>: InitialAndLast<Input>[1]

Last value of an ArrayLike.

Remarks

Type of the last character of a string or the last element of an array.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const last: Last<typeof array> = "💚";

See

ArrayLike
InitialAndLast

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	The input `ArrayLike`.

LocaleIdentifier

Ƭ LocaleIdentifier: "eo" | "yue-Hant-HK" | LocaleString<"af", `${“N” | “Z”}A`> | LocaleString<"ak", "GH"> | LocaleString<"am", "ET"> | LocaleString<"ar", `${“A” | “Y”}E` | "BH" | "DZ" | `E${“G” | “H” | “R”}` | `I${“L” | “Q”}` | "JO" | "KW" | `I${“B” | “Y”}` | `M${“A” | “R”}` | "OM" | "PS" | "QA" | `S${“A” | “D” | “O” | “S” | “Y”}` | `T${“D” | “N”}`> | LocaleString<"as", "IN"> | LocaleString<"asa", "TZ"> | LocaleString<"az", LocaleString<"Cyrl" | "Latn", "AZ">> | LocaleString<"be", "BY"> | LocaleString<"bem", "ZM"> | LocaleString<"bez", "TZ"> | LocaleString<"bg", "BG"> | LocaleString<"bm", "ML"> | LocaleString<"bn", "BD" | "IN"> | LocaleString<"bo", `${“C” | “I”}N`> | LocaleString<"bs", "BA"> | LocaleString<"ca", "ES"> | LocaleString<"cgg", "UG"> | LocaleString<"chr", "US"> | LocaleString<"cs", "CZ"> | LocaleString<"cy", "GB"> | LocaleString<"da", "DK"> | LocaleString<"dav", "KE"> | LocaleString<"de", "AT" | `${“B” | “D”}E` | "CH" | `L${“I” | “U”}`> | LocaleString<"ebu", "KE"> | LocaleString<"ee", "GH" | "TG"> | LocaleString<"el", "CY" | "GR"> | LocaleString<"en", `A${“S” | “U”}` | `B${“E” | “W” | “Z”}` | "CA" | `G${“B” | “U”}` | "HK" | "IE" | `I${“L” | “N”}` | "JM" | `M${“H” | “P” | “T” | “U”}` | `N${“A” | “Z”}` | `P${“H” | “K”}` | "SG" | "TT" | `U${“M” | “S”}` | "VI" | `Z${“A” | “W”}`> | LocaleString<"es", "419" | "AR" | "BO" | `C${“L” | “O” | “R”}` | "DO" | `E${“C” | “S”}` | `G${“Q” | “T”}` | "HN" | "MX" | "NI" | `P${“A” | “E” | “R” | “Y”}` | "SV" | `U${“S” | “Y”}` | "VE"> | LocaleString<"et", "EE"> | LocaleString<"eu", "ES"> | LocaleString<"fa", "AF" | "IR"> | LocaleString<"ff", "SN"> | LocaleString<"fi", "FI"> | LocaleString<"fil", "PH"> | LocaleString<"fo", "FO"> | LocaleString<"fr", `B${“E” | “F” | “I” | “J” | “L”}` | `C${“A” | “D” | “F” | “G” | “H” | “I” | “M”}` | "DJ" | "FR" | `G${“A” | “N” | “P” | “Q”}` | "KM" | "LU" | `M${“C” | “F” | “G” | “L” | “Q”}` | "NE" | `R${“E” | “W”}` | "SN" | `T${“D” | “G”}`> | LocaleString<"ga", "IE"> | LocaleString<"gl", "ES"> | LocaleString<"gsw", "CH"> | LocaleString<"gu", "IN"> | LocaleString<"guz", "KE"> | LocaleString<"gv", "GB"> | LocaleString<"ha", LocaleString<"Latn", "GH" | `N${“E” | “G”}`>> | LocaleString<"haw", "US"> | LocaleString<"he", "IL"> | LocaleString<"hi", "IN"> | LocaleString<"hr", "HR"> | LocaleString<"hu", "HU"> | LocaleString<"hy", "AM"> | LocaleString<"id", "ID"> | LocaleString<"ig", "NG"> | LocaleString<"ii", "CN"> | LocaleString<"is", "IS"> | LocaleString<"it", "CH" | "IT"> | LocaleString<"ja", "JP"> | LocaleString<"jmc", "TZ"> | LocaleString<"ka", "GE"> | LocaleString<"kab", "DZ"> | LocaleString<"kam", "KE"> | LocaleString<"kde", "TZ"> | LocaleString<"kea", "CV"> | LocaleString<"khq", "ML"> | LocaleString<"ki", "KE"> | LocaleString<"kk", LocaleString<"Cyrl", "KZ">> | LocaleString<"kl", "GL"> | LocaleString<"kln", "KE"> | LocaleString<"km", "KH"> | LocaleString<"kn", "IN"> | LocaleString<"ko", "KR"> | LocaleString<"kok", "IN"> | LocaleString<"kw", "GB"> | LocaleString<"lag", "TZ"> | LocaleString<"lg", "UG"> | LocaleString<"lt", "LT"> | LocaleString<"luo", "KE"> | LocaleString<"luy", "KE"> | LocaleString<"lv", "LV"> | LocaleString<"mas", "KE" | "TZ"> | LocaleString<"mer", "KE"> | LocaleString<"mfe", "MU"> | LocaleString<"mg", "MG"> | LocaleString<"mk", "MK"> | LocaleString<"ml", "IN"> | LocaleString<"mr", "IN"> | LocaleString<"ms", "BN" | "MY"> | LocaleString<"mt", "MT"> | LocaleString<"my", "MM"> | LocaleString<"naq", "NA"> | LocaleString<"nb", "NO"> | LocaleString<"nd", "ZW"> | LocaleString<"ne", "IN" | "NP"> | LocaleString<"nl", "BE" | "NL"> | LocaleString<"nn", "NO"> | LocaleString<"nyn", "UG"> | LocaleString<"om", "ET" | "KE"> | LocaleString<"or", "IN"> | LocaleString<"pa", LocaleString<"Arab", "PK"> | LocaleString<"Guru", "IN">> | LocaleString<"pl", "PL"> | LocaleString<"ps", "AF"> | LocaleString<"pt", "BR" | "GW" | "MZ" | "PT"> | LocaleString<"rm", "CH"> | LocaleString<"ro", "MD" | "RO"> | LocaleString<"rof", "TZ"> | LocaleString<"ru", "MD" | "RU" | "UA"> | LocaleString<"rw", "RW"> | LocaleString<"rwk", "TZ"> | LocaleString<"saq", "KE"> | LocaleString<"seh", "MZ"> | LocaleString<"ses", "ML"> | LocaleString<"sg", "CF"> | LocaleString<"shi", LocaleString<"Latn" | "Tfng", "MA">> | LocaleString<"si", "LK"> | LocaleString<"sk", "SK"> | LocaleString<"sl", "SI"> | LocaleString<"sn", "ZW"> | LocaleString<"so", "DJ" | "ET" | "KE" | "SO"> | LocaleString<"sq", "AL"> | LocaleString<"sr", LocaleString<"Cyrl" | "Latn", "BA" | "ME" | "RS">> | LocaleString<"sv", "FI" | "SE"> | LocaleString<"sw", "KE" | "TZ"> | LocaleString<"ta", "IN" | "LK"> | LocaleString<"te", "IN"> | LocaleString<"teo", "KE" | "UG"> | LocaleString<"th", "TH"> | LocaleString<"ti", `E${“R” | “T”}`> | LocaleString<"to", "TO"> | LocaleString<"tr", "TR"> | LocaleString<"tzm", LocaleString<"Latn", "MA">> | LocaleString<"uk", "UA"> | LocaleString<"ur", "IN" | "PK"> | LocaleString<"uz", LocaleString<"Arab", "AF"> | LocaleString<"Cyrl" | "Latn", "UZ">> | LocaleString<"vi", "VN"> | LocaleString<"vun", "TZ"> | LocaleString<"xog", "UG"> | LocaleString<"yo", "NG"> | LocaleString<"zh", LocaleString<`Han${“s” | “t”}`, "HK" | "MO"> | LocaleString<"Hans", "CN" | "SG"> | LocaleString<"Hant", "TW">> | LocaleString<"zu", "ZA">

Locale identifiers (language-country).

Remarks

When using i18n tools, this is a stricter union type than string to handle the locale identifiers.

Example

1
const locale: LocaleIdentifier = "en-US";

See

EmptyString

LocaleString

Ƭ LocaleString<LanguageCode, CountryCodes, Separator>: `${LanguageCode}${MaybeEmpty<`${Separator}${CountryCodes}`>}`

String for locales such as “en-US”.

Remarks

This type mainly exists to make LocaleIdentifier a little bit easier to the eyes.

Example

1
type English1: LocaleIdentifier<"en", "US" | "UK">; // "en" | "en-US" | "en-UK"
2
type English2: LocaleIdentifier<"en", "US" | "UK", "_">; // "en" | "en_US" | "en_UK"

See

LocaleIdentifier

Type parameters

Name	Type	Description
`LanguageCode`	extends `MultiCharacterString`	2 character language code.
`CountryCodes`	extends `MultiCharacterString`	Union of country codes.
`Separator`	extends `"-"` \| `"_"` = `"-"`	-

MaybeEmpty

Creates an union of the given type with a possible “empty” value.

Remarks

This type is useful to make clear that we expect a possible empty value.

Example

1
type Greet: MaybeEmpty<"Hello">; // "Hello" | ""
2
type Triple: MaybeEmpty<readonly [1, 2, 3]>; // readonly [1, 2, 3] | readonly []
3
type Foo: MaybeEmpty<{ readonly foo: "bar" }>; // { readonly foo: "bar" } | {}

See

Either
EmptyArray
EmptyRecord
EmptyString

Type parameters

Name	Description
`Input`	Type to unite with it’s empty counterpart.

MultiCharacterString

Ƭ MultiCharacterString: `${string}${string}`

String with more than 1 character on it.

Deprecated

Not actually deprecated, this type doesn’t do anything yet.

Remarks

This type will be useful when a given string will need more than one character on it. Sadly this type doesn’t work because TypeScript considers "" a string, so "" + "" === string, same for "f" + "" which is not a multi character string.

Example

1
const test1: MultiCharacterString = "foo"; // ok
2
const test2: MultiCharacterString = "f"; // error

MultiDigitNumberString

Ƭ MultiDigitNumberString: `${bigint}${bigint}`

String with more than 1 number on it.

Remarks

This type is useful when a given string will need more than one number on it.

Example

1
const test1: MultiDigitNumberString = "01"; // ok
2
const test2: MultiDigitNumberString = "1"; // error

NotEmpty

Ƭ NotEmpty<Type>: Exclude<Type, Empty>

Type for a non-empty ArrayLike, object or string.

Remarks

Example

1
const notEmptyString: NotEmpty<string> = "🟢";
2
const notEmptyArray: NotEmpty<ReadOnlyArray> = ["🟢", "🟩"];
3
const notEmptyRecord: NotEmpty<ReadOnlyRecord> = { "🟢": "🟩" };

See

Empty

Type parameters

Name	Type	Description
`Type`	extends `ArrayLike` \| `object` \| `string`	The type to check.

Tagger

Ƭ Tagger<Output, Expressions>: (templateStrings: TemplateStringsArray, …expressions: Expressions) => Output

Tag function for tagged templates.

Remarks

Type to represent a tag function for tagged templates, which takes a TemplateStringArray and any number of expressions, and returns a value of type Output (string by default).

Example

1
const intParser: Tagger<number> = strings => parseInt(strings.join(""), 10);
2
intParser`100`; // 100

See

ReadOnlyArray

Type parameters

Name	Type	Description
`Output`	`string`	Type of the output value.
`Expressions`	extends `ReadOnlyArray` = `ReadOnlyArray`	Type of the expressions.

Type declaration

▸ (templateStrings, ...expressions): Output

Parameters

Name	Type
`templateStrings`	`TemplateStringsArray`
`...expressions`	`Expressions`

Returns

Output

Tail

Ƭ Tail<Input>: HeadAndTail<Input>[1]

Last values of an ArrayLike (omitting the first).

Remarks

Type of the last items of an ArrayLike, excluding the first item in said ArrayLike.

Example

1
const array = ["🟢", "🟩", "💚"];
2
const tail: Tail<typeof array> = ["🟩", "💚"];

See

ArrayLike
HeadAndTail

Type parameters

Name	Type	Description
`Input`	extends `ArrayLike`	Type of the array to get the tail.