types-kit.ifextends.md

September 4, 2023 ยท View on GitHub

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IfExtends type

If Condition[0] extends Condition[1], return Case1, else return Case2.

Signature:

export type IfExtends<Condition extends [unknown, unknown], Case1, Case2> = [
  Condition[0],
] extends [Condition[1]]
  ? Case1
  : Case2

Example

 // Expect: 1
 type Foo = IfExtends<[true, boolean], 1, 2>