Skip to main content
{} stackoverfun

Type Signature · #21 · 2026-04-25

What is the type of `len`?

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 | null) {
  const len = x!.length;
  return len;
}

Loading your progress...

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