From a static dictionary of strings, infer a type/interface describing the dictionary precisely, using string literals for value types

Question

I have a static dictionary:

const myDict = {
  1: "one",
  2: "two"
}

The default inferred type for this is Record<1 | 2, string>.

I would like to derive a type that only accepts the exact string literals assigned to myDict properties:

type T = {
  1: typeof "one",
  2: typeof "two"
}

How can I derive such type? Typing the original dictionary (so typeof myDict would equal to my desired type) would work the best for me.

---

I know I can assert the type via as keyword:

const myDict = {
  1: "one" as typeof "one",
  2: "two" as typeof "two"
}

but this workaround is very impractical and prone to error with large dictionaries. What would be a better approach?

Answer 1

You can accomplish this using a const assertion.

const myDict = {
  1: "one",
  2: "two",
} as const