Typescript 递归推断 object 值

Question

Let's say I have this AnalyticsService class

export class AnalyticsService {
  static sendAnalytics(eventName: string) {
    console.log(eventName);
    // logic here...
  }

  static EVENTS = {
    Header: {
      LogoClicked: "Header: Logo Clicked",
    },
    UserMenu: {
      LoginButtonClicked: "User Menu: Login Button Clicked",
      LogoutButtonClicked: "User Menu: Logout Button Clicked",
    }
  };
}

And I use this class to send analytics like:

AnalyticsService.sendAnalytics(AnalyticsService.EVENTS.Header.LogoClicked)

I want to extract all values of EVENTS to a union type to make sure that sendAnalytics function gets only existing event names

for example, the results here should be: "Header: Logo Clicked" | "User Menu: Login Button Clicked" | "User Menu: Logout Button Clicked" "Header: Logo Clicked" | "User Menu: Login Button Clicked" | "User Menu: Logout Button Clicked"

Is it even possible with typescript?

If it is, is it going to significantly reduce the typescript performance when it's a pretty big object?

Edit : just to clarify the EVENTS object can be really nested (I gave a tiny example just for simplicity )

Answer 1

Here is how you could do to correctly type sendAnalytics :

type Keys = typeof AnalyticsService.EVENTS[keyof typeof AnalyticsService.EVENTS]

type UnionToIntersection<U> =
  (U extends any ? (k: U) => void : never) extends ((k: infer I) => void) ? I : never

type FlattenedEvents = UnionToIntersection<Keys>;

type EventNames = FlattenedEvents[keyof FlattenedEvents];

export class AnalyticsService {
  static sendAnalytics(eventName: EventNames) {
    console.log(eventName);
    // logic here...
  }

  static EVENTS = {
    Header: {
      LogoClicked: "Header: Logo Clicked",
    },
    UserMenu: {
      LoginButtonClicked: "User Menu: Login Button Clicked",
      LogoutButtonClicked: "User Menu: Logout Button Clicked",
    }
  } as const;
}

AnalyticsService.sendAnalytics(AnalyticsService.EVENTS.Header.LogoClicked); // OK
AnalyticsService.sendAnalytics('test'); // KO

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