typescript_advanced

Pick creates a type with selected properties, such as Pick<User, 'id' | 'name'>, while Omit excludes properties, like Omit<User, 'password'>. Both derive new types from existing interfaces without redefining fields.

Define a schema with z.object containing field validators, then derive the static type using z.infer<typeof Schema>. This gives runtime validation and compile-time types from a single source of truth.

Use interface for object structures since it supports declaration merging and extension. Use type aliases for unions, conditional types, and complex computed types that interfaces cannot express.

unknown is the type-safe counterpart of any because it forces type narrowing before use. Replace any with unknown and narrow it using type guards like is or in operators.

Use discriminated unions when modeling mutually exclusive states, such as success and error results. A shared literal field like success: true | false lets the compiler narrow types automatically in conditionals.