How do I get Enum key from a value in Typescript?

I'm having this problem in a large project, so I've tried to simplify my problem to this example:

enum Screens {
    Home,
    About
}

interface HomeData {
    title: string
    posts: string[]
}

interface AboutData {
    title: string
}

interface PageData {
    [Screens.Home]: HomeData
    [Screens.About]: AboutData
}

const pageData: PageData = {
    [Screens.Home]: { title: 'Home', posts: ['intro', 'care'] },
    [Screens.About]: { title: 'Home' }
}

const addData = (screen: Screens, data: PageData[typeof screen]) => {
    pageData[screen] = data; //error here, Type 'HomeData | AboutData' is not assignable to type 'HomeData & AboutData'.
}

Im trying to dynamically pass the data object to the function and assign it to the corresponding screen, but typescript dosen't seem to understand that pageData[screen] is tied to the first argument of the function: screen, it thinks that the argument data must satisfy HomeData & AboutData.

I know there are probably other ways to implement this, but my codebase is very intertwined to this structure.

You can use the generic parameter for the screen and get the data of that specific screen:

const addData = <T extends Screens>(screen: T, data: PageData[T]) => {
  pageData[screen] = data;
};

Usage:

addData(Screens.Home, { posts: [], title: "" }); // no error
addData(Screens.About, { posts: [], title: "" }); // expected error

playground