如何键入 object，其键是另一种类型键的子集

Question

I have a type like this:

type Metadata = {
  name: string;
  size: number;
  date: string;
  language: string;
  formattedName: string;
  normalizedDate: string
};

and now I need to build this constant:

const main = {
  name: ["main", "master"],
  size: ["size"],
  date: ["date"],
  language: ["lang", "language"]
} as ??? // as Record<keyof Metadata, string[]>;

that is an object whose keys are a subset of the keys of the type Metadata and the values are an array of string. How can I type the main object? I tried Partials(Metadata) but it seems to be not right. Which is the right way to do that?

Answer 1

You can say that this type must "satisfy" or be at least assignable to another type, without actually overriding the inferred type information with the new satisfies keyword in 4.9+:

const main = {
  name: ["main", "master"],
  size: ["size"],
  date: ["date"],
  language: ["lang", "language"]
} satisfies Partial<Record<keyof Metadata, string[]>>;