TypeScript · Junior · Question 58 of 75

Why can't you check `if (data is User)` at runtime?

✓Correct answer: Types are erased during compilation; to check external data at runtime you need code (a type guard or a schema like Zod)
2Because is is reserved for classes
3You can - TypeScript adds runtime checks automatically

Explanation

TypeScript only checks code at compile time. Data from APIs, localStorage or forms must be validated by real code.

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