type-plus
Version:
Provides additional types for TypeScript.
61 lines • 1.93 kB
TypeScript
import type { IsAny } from '../any/any_type.js';
/**
* Check if the type `T` is exactly `string`.
*
* ```ts
* type R = StrictStringType<string> // string
*
* type R = StrictStringType<''> // never
* type R = StrictStringType<'1'> // never
* type R = StrictStringType<string | boolean> // never
* type R = StrictStringType<never> // never
* type R = StrictStringType<unknown> // never
* ```
*/
export type StrictStringType<T, Then = T, Else = never> = IsAny<T, Else, [
T,
string
] extends [string, T] ? Then : Else>;
/**
* Is the type `T` exactly `string`.
*
* ```ts
* type R = IsStrictString<string> // true
*
* type R = IsStrictString<''> // false
* type R = IsStrictString<'a'> // false
* type R = IsStrictString<string | boolean> // false
* type R = IsStrictString<never> // false
* type R = IsStrictString<unknown> // false
* ```
*/
export type IsStrictString<T, Then = true, Else = false> = StrictStringType<T, Then, Else>;
/**
* Check if the type `T` is not exactly `string`.
*
* ```ts
* type R = NotStrictStringType<string> // never
*
* type R = NotStrictStringType<''> // ''
* type R = NotStrictStringType<'a'> // 'a'
* type R = NotStrictStringType<string | boolean> // string | boolean
* type R = NotStrictStringType<never> // never
* type R = NotStrictStringType<unknown> // unknown
* ```
*/
export type NotStrictStringType<T, Then = T, Else = never> = StrictStringType<T, Else, Then>;
/**
* Is the type `T` not exactly `string`.
*
* ```ts
* type R = IsNotStrictString<string> // false
*
* type R = IsNotStrictString<''> // true
* type R = IsNotStrictString<'a'> // true
* type R = IsNotStrictString<string | boolean> // true
* type R = IsNotStrictString<never> // true
* type R = IsNotStrictString<unknown> // true
* ```
*/
export type IsNotStrictString<T, Then = true, Else = false> = StrictStringType<T, Else, Then>;
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