Type Signature · #5 · 2026-04-09

What is the return type of `f`?

TypeScript ·Difficulty 1/3

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.

function f(x: string | number) {
  if (typeof x === 'string') return x.length;
  return x;
}

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