Typescript 传播到文字类型数组中

发布于03月29日

我想在Typescript中实现这一点:

type animals = 'cat' | 'dog'

let selectedAnimals: animals[] = ['cat']

selectedAnimals = [ // <- Type 'string[]' is not assignable to type 'animals[]'
    ...selectedAnimals,
    ...(condition ? ['cat'] : [])
]

Link.

下面的方法很有效，但是有没有比使用as animals更好的方法呢？

type animals = 'cat' | 'dog'

let selectedAnimals: animals[] = ['cat']

selectedAnimals = [
    ...selectedAnimals,
    ...(['cat' as animals]),
    ...(['wednesday' as animals]) // <- this also compiles
]

推荐答案

您可以将as const添加到['cat']，使其类型为readonly ["cat"]，而不是string[]，代码将在编译时不会丢失类型安全性.这也将防止包括非动物数组:

type animals = 'cat' | 'dog'

let selectedAnimals: animals[] = ['cat']

selectedAnimals = [
    ...selectedAnimals,
    ...(['cat'] as const),
    // ...(['wednesday'] as const) // <- will fail
]

TypeScript playground

或者，您可以将as const添加到单个元素中，例如[`cat` as const]，它将数组键入"cat"[].(Playground)