Validate a signup form in TypeScript
TypeScript interview exercise on Practical, difficulty 2 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Write validateSignup({ name, email, age }) that returns an errors object. Rules: name is required (non-blank); email must look like an email; age, if provided, must be a number ≥ 13. Only failing fields appear in the result.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.