TypeScript Utility Types: Partial, Pick, Omit, and 8 More You'll Actually Use

TypeScript's utility types are generic types built into the language for transforming existing types. Most developers know Partial and Readonly. Fewer know Record, Exclude, and ReturnType — and those are often the ones that save the most code.

Partial<T>

Makes all properties of T optional. Most useful for update functions where you only want to specify the fields being changed: `function updateUser(id: string, updates: Partial<User>)`. Without Partial, you'd have to manually define a separate type with every field optional.

Required<T>

The inverse — makes all optional properties required. Useful when you have a type with optional fields in general use but need a version where everything must be present (like after validation).

Pick<T, K>

Creates a type with only the specified keys from T. `Pick<User, 'id' | 'email'>` gives you a type with just `id` and `email`. Useful for API responses where you don't want to expose all fields of an internal type.

Omit<T, K>

The inverse of Pick — creates a type with everything except the specified keys. `Omit<User, 'passwordHash'>` is a common pattern for creating public-facing versions of types with sensitive fields removed.

Record<K, V>

Creates an object type with keys of type K and values of type V. `Record<string, number>` is a dictionary. `Record<UserId, User>` creates a lookup map. Far cleaner than `{ [key: string]: number }` and allows narrower key types.

ReturnType<T>

Extracts the return type of a function. Useful when you want the type of whatever a function returns without duplicating the type definition. If the function's return type changes, ReturnType picks it up automatically.

Exclude<T, U> and Extract<T, U>

Exclude removes members of a union type: `Exclude<'a' | 'b' | 'c', 'a'>` gives `'b' | 'c'`. Extract keeps only the specified members. Both are most useful when working with union types and you need variants of them for different contexts.

NonNullable<T>

Removes null and undefined from a type. `NonNullable<string | null | undefined>` gives `string`. Most useful after null checks when you've already verified the value exists and want to communicate that to the type system.