Type Signature · #47 · 2026-05-21
What is 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 Concat<A extends unknown[], B extends unknown[]> = [...A, ...B];
type R = Concat<[1, 2], [3, 4]>;
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