type boolean - nberlette/is GitHub Wiki

@nick/is/type/boolean

IsBoolean

Signature

export type IsBoolean<T, True = true, False = false> = [T] extends [boolean]
  ? [boolean] extends [T] ? True : False
  : False;

Checks if the type T is the generic type boolean, returning True if it is, and False if not.

This predicate is not satisfied by just true or false; the type must be a union of both (true | false, which is what the boolean type actually represents) to result in a positive match.

Type Parameters
  • T
  • True (default: true)
  • False (default: false)
Categories

Types Boolean

Examples

import type { IsBoolean } from "@nick/is/type/boolean";

type A = IsBoolean<true>; // false
type B = IsBoolean<false>; // false
type C = IsBoolean<boolean | 0>; // false

type Y = IsBoolean<true | false>; // true
type Z = IsBoolean<boolean>; // true

IsFalse

Signature

export type IsFalse<T, True = true, False = false> = [T, false] extends
  [false, T] ? True : False;

Checks if the type T is specifically false, returning True if it is, and False if not.

Type Parameters
  • T
  • True (default: true)
  • False (default: false)
Categories

Types Boolean

Examples

import type { IsFalse } from "@nick/is/type/boolean";

type A = IsFalse<true>; // false
type B = IsFalse<false>; // true
type C = IsFalse<boolean>; // false

IsTrue

Signature

export type IsTrue<T, True = true, False = false> = [T, true] extends [true, T]
  ? True
  : False;

Checks if the type T is specifically true, returning True if it is, and False if not.

Type Parameters
  • T
  • True (default: true)
  • False (default: false)
Categories

Types Boolean

Examples

import type { IsTrue } from "@nick/is/type/boolean";

type A = IsTrue<true>; // true
type B = IsTrue<false>; // false
type C = IsTrue<boolean>; // false
⚠️ **GitHub.com Fallback** ⚠️