If<T, ToCheck, True, False>
ts
type If<T, ToCheck, True, False> = T extends ToCheck ? True : False;Defined in: types.ts:59
Conditional type that returns true if T extends ToCheck, otherwise returns false.
Type Parameters
| Type Parameter | Default type | Description |
|---|---|---|
T | - | The type to check |
ToCheck | - | The type to check against |
True | true | The type to return if the condition is true (default: true) |
False | false | The type to return if the condition is false (default: false) |
Example
ts
type A = If<string, string, 'yes', 'no'>; // 'yes'
type B = If<string, number, 'yes', 'no'>; // 'no'