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Manuals / TypeScript / Chapter 7

C · Reuse · intermediate · Week 3–4 · Chapter 7 of 11

Utility types

Built-in type transformers: Partial, Required, Pick, Omit, Record, Readonly, ReturnType, Parameters. Compose them for DRY API types. keyof and indexed access types unlock advanced patterns.

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Partial and Required

Partial<User> makes all fields optional — update DTOs. Required<User> opposite — after validation.

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Do this now

Create UpdateUserInput = Partial<Pick<User, "name" | "email">>.

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Chapter learning outcomes
  • Partial & Required
  • Pick & Omit
  • Record & Readonly
  • ReturnType & Parameters
  • keyof patterns

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Side quest

Form types

CreateUserForm = Omit<User, "id"|"createdAt">. UpdateUserForm = Partial<CreateUserForm>. Wire to mock handlers.