safe-dictionary

SafeDictionary<Type, Keys?> constructs an optional object type which property keys are Keys (string by default) and which property values are Type

Like Partial<Record<Keys, Type>>, but can be used with only one argument:

const abbreviations: SafeDictionary<string> = {
  afaik: "as far as I know",
  afk: "away from keyboard",
};

It ensures type safety of index access:

const { til } = abbreviations;
//      ^? string | undefined

It also doesn't enforce key exhaustiveness:

interface CatInfo {
  age: number;
  breed: string;
}

type CatName = "miffy" | "boris" | "mordred";

const cats: SafeDictionary<CatInfo, CatName> = {
  miffy: { age: 10, breed: "Persian" },
  boris: { age: 5, breed: "Maine Coon" },
  // 'mordred' key is not specified and there is no TS error
};

TS Playground – https://tsplay.dev/WJ7eZw