Quiz · 3 questions
🪢 Unions & Intersections — Combining Types
A | B, A & B, discriminated unions, exhaustiveness, distribution
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Quiz
01What does
string | number describe?Hint
After
if (typeof x === 'string') { /* x is string here */ }, the compiler narrows automatically.02What is a discriminated union?
Hint
The discriminator field's type is what makes narrowing work — it must be a literal type so each variant has a different value.
03What does it mean that conditional types are 'distributive' over unions?
Hint
Distribution is one of those features where it'd be confusing without examples — write a small conditional type, apply it to a union, and observe what comes out.
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