Type Signature · #94 · 2026-07-07

What is the type of `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.

class Builder {
  private items: string[] = [];
  add(item: string): this {
    this.items.push(item);
    return this;
  }
}
class FancyBuilder extends Builder {
  bold() { return this; }
}
const r = new FancyBuilder().add('x');

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