Which built-in utility types do you use most, and what do they do?

Summary

Common ones: Partial<T>, Required<T>, Readonly<T>, Pick<T, K>, Omit<T, K>, Record<K, V>, Exclude<U, X>, Extract<U, X>, NonNullable<T>, ReturnType<F>, Parameters<F>, Awaited<T> and NoInfer<T> (5.4).

Longer Answer

They're built with mapped and conditional types. Example uses: Partial<User> for PATCH payloads, Omit<User, 'password'> for public DTOs, Record<Status, string> for exhaustive lookup tables, ReturnType<typeof createStore> to derive types from implementations, and Awaited<ReturnType<typeof fetchUser>> for async results.

Code Example

interface User { id: string; name: string; email: string; password: string }

type PublicUser = Omit<User, "password">;
type UserPatch = Partial<Pick<User, "name" | "email">>;
type StatusLabels = Record<"active" | "banned", string>;

async function fetchUser(id: string): Promise<PublicUser> { /* ... */ return null!; }
type Fetched = Awaited<ReturnType<typeof fetchUser>>; // PublicUser

Key Points

• Partial/Required/Readonly modify properties
• Pick/Omit select keys
• Record for maps with known keys
• ReturnType/Parameters/Awaited derive types