If

Since 1.1.0

If-then-else at the type level.

Signature

type If<C extends boolean, T, F> = C extends true ? T : F

Parameters

Parameter	Description
C	The condition (boolean type)
T	Type returned when condition is true
F	Type returned when condition is false

Examples

Basic Usage

import type { If } from 'uni-types'

type A = If<true, string, number>    // string
type B = If<false, string, number>   // number

With Type Predicates

import type { If, IsAny } from 'uni-types'

type SafeResult<T> = If<IsAny<T>, never, T>

type A = SafeResult<string>  // string
type B = SafeResult<any>     // never

Conditional Logic

import type { If, And, Or } from 'uni-types'

type Result<A extends boolean, B extends boolean> = If<
  Or<A, B>,
  'at least one is true',
  'both are false'
>

Related

• Not - Logical NOT
• And - Logical AND
• Or - Logical OR