type-plus
Version:
Provides additional types for TypeScript.
56 lines • 1.69 kB
TypeScript
import type { IsAnyOrNever } from '../mix_types/any_or_never_type.js';
/**
* Check if the type `T` is `boolean`, including `true` and `false`.
*
* ```ts
* type R = BooleanType<boolean> // boolean
* type R = BooleanType<true> // true
* type R = BooleanType<false> // false
*
* type R = BooleanType<number> // never
* type R = BooleanType<unknown> // never
* ```
*/
export type BooleanType<T, Then = T, Else = never> = IsAnyOrNever<T, Else, [
T
] extends [boolean] ? Then : Else>;
/**
* Check if the type `T` is not `boolean`, including `true` and `false`.
*
* ```ts
* type R = NotBooleanType<boolean> // never
* type R = NotBooleanType<true> // never
* type R = NotBooleanType<false> // never
*
* type R = NotBooleanType<number> // number
* type R = NotBooleanType<unknown> // unknown
* ```
*/
export type NotBooleanType<T, Then = T, Else = never> = BooleanType<T, Else, Then>;
/**
* Is the type `T` `boolean`, including `true` and `false`.
*
* ```ts
* type R = IsBoolean<boolean> // true
* type R = IsBoolean<true> // true
* type R = IsBoolean<false> // true
*
* type R = IsBoolean<number> // false
* type R = IsBoolean<unknown> // false
* ```
*/
export type IsBoolean<T, Then = true, Else = false> = BooleanType<T, Then, Else>;
/**
* Is the type `T` not `boolean`, including `true` and `false`.
*
* ```ts
* type R = IsNotBoolean<boolean> // false
* type R = IsNotBoolean<true> // false
* type R = IsNotBoolean<false> // false
*
* type R = IsNotBoolean<number> // true
* type R = IsNotBoolean<unknown> // true
* ```
*/
export type IsNotBoolean<T, Then = true, Else = false> = BooleanType<T, Else, Then>;
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