Index signatures

Index signatures are used to express the shape of key/value pairs.

type Fruit = "apple" | "banana" | "orange";

type Prices = {
  [index: Fruit]: number;
};

// This is equivalent to
type Prices = Record<Fruit, number>;

See index signatures in the TypeScript documentation

So to make a mapping between Fruits and Prices, it looks like:

type FruitPriceMapping = {
  [key: Fruit]: Price;
};

const MAPPING: FruitPriceMapping = {
  apple: { value: 25, currency: "aud" },
  /* and others go here */
};

Alternatively, TypeScript has the Record utility type, which you could consider more terse:

type FruitPriceMapping = Record<Fruit, Price>;