Type alias IsFunction<T, $O>

🎭 predicate

Validate if T is Function or function signature.

Example

type R = IsFunction<Function> // true
type R = IsFunction<() => void> // true

type R = IsFunction<never> // false
type R = IsFunction<unknown> // false
type R = IsFunction<number> // false

type R = IsFunction<Function | number> // boolean
type R = IsFunction<(() => string) | number> // boolean
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🔢 customize

Filter to ensure T is Function or function signature, otherwise returns never.

Example

type R = IsFunction<Function, { selection: 'filter' }> // Function
type R = IsFunction<() => void, { selection: 'filter' }> // () => void

type R = IsFunction<never, { selection: 'filter' }> // never
type R = IsFunction<unknown, { selection: 'filter' }> // never
type R = IsFunction<Function | number, { selection: 'filter' }> // Function

type R = IsFunction<(() => string) | number, { selection: 'filter' }> // () => string
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🔢 customize:

Disable distribution of union types.

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

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

Example

type R = IsFunction<Function, $SelectionBranch> // $Then
type R = IsFunction<string, $SelectionBranch> // $Else
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