Type Signature · #45 · 2026-05-19

What is the type of property `a.b.c` in type `R`?

TypeScript ·Difficulty 3/3

How to play

Read the TypeScript snippet and pick the correct type from four choices. Think about inference, narrowing, and utility types. Press 1–4 or click to answer.

type DeepPartial<T> = {
  [K in keyof T]?: T[K] extends object ? DeepPartial<T[K]> : T[K];
};
type Nested = { a: { b: { c: number } } };
type R = DeepPartial<Nested>;

Loading your progress...

Press 1 through 4, or tap a numbered choice, to answer. Back to hub