要求 A 类型是 Typescript 中 B 类型数组中的字符串

Question

I have a type that looks like this:

type MyType = {
  tabs: string[];
  activeTab: string;
}

I want to require that activeTab is a member of tabs . Is there a way to do this with generics?

Answer 1

Sure can. Just accept a generic parameter that is a union of all possible strings.

type MyType<Tab extends string> = {
  tabs: Tab[];
  activeTab: Tab;
}

const a: MyType<'asd' | 'qwe'> = {
  tabs: ['asd', 'qwe'],
  activeTab: 'asd'
}

const b: MyType<'asd' | 'qwe'> = {
  tabs: ['asd', 'qwe'],
  activeTab: 'nope' // Type '"nope"' is not assignable to type '"asd" | "qwe"'
}

Playground