Type alias IsBoolean<T, $O>

🎭 predicate

Validate if T is boolean, including true and false.

Example

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
type R = IsBoolean<string | boolean> // boolean
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🔢 customize

Filter to ensure T is boolean, including true and false, otherwise returns never.

Example

type R = IsBoolean<boolean, { selection: 'filter' }> // boolean
type R = IsBoolean<true, { selection: 'filter' }> // true
type R = IsBoolean<false, { selection: 'filter' }> // true

type R = IsBoolean<number, { selection: 'filter' }> // never
type R = IsBoolean<unknown, { selection: 'filter' }> // never
type R = IsBoolean<never, { selection: 'filter' }> // never
type R = IsBoolean<string | boolean, { selection: 'filter' }> // boolean
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🔢 customize:

Disable distribution of union types.

type R = IsBoolean<boolean | 1> // boolean
type R = IsBoolean<boolean | 1, { distributive: false }> // false
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🔢 customize

Use unique branch identifiers to allow precise processing of the result.

Example

type R = IsBoolean<boolean, $SelectionBranch> // $Then
type R = IsBoolean<string, $SelectionBranch> // $Else
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