typescript - 如何在 Typescript 中输入 es6 对象/字典

Question

例如，我有以下类型，我使用 es6 对象作为字典。

type User = {
    id: string,
    name: string   
}
const usersDict = { [key: string]: User  } = {}

但问题是，如果我尝试获取一个不存在的用户 ID，则上面的输入是不正确的。例如

const user = usersDict['user_id_that_doesnt_exist'] // type of user is User

我应该像下面这样输入 usersDict 吗？

const usersDict = { [key: string]: User | undefined } = {}

这一个的问题是在下面的例子中循环遍历值

const usersDict = { [key: string]: User | undefined } = {}
Object.values(usersDict).map((user)=>{
    // here the type of user is User|undefined, 
    // but it really should be just User type,
    // since it's impossible to be undefined
})

Answer 1

如果可以使用noUncheckedIndexAccess在你的 tsconfig 然后你会得到 all the behavior you want :

type User = {
  id: string,
  name: string
}

type UserDictionary = {
  [userId: string]: User
}

const usersDict: UserDictionary = {};

const user = usersDict['user_id_that_doesnt_exist'] // type of user is User | undefined

Object.values(usersDict).map((user)=>{
    // here the type of user is User, as desired
})