Utility Types

Intro to Utility Types
Intro to Utility Types
TypeScript provides powerful utility types that let you transform and manipulate types. These built-in helpers reduce boilerplate and make your types more expressive.
type Event = { id: string; title: string; startsAt: Date; location?: string }

// Make all properties optional
type DraftEvent = Partial<Event>
// { id?: string; title?: string; startsAt?: Date; location?: string }

// Select specific properties
type EventSummary = Pick<Event, 'id' | 'title'>
// { id: string; title: string }

// Remove specific properties
type PublicEvent = Omit<Event, 'location'>
// { id: string; title: string; startsAt: Date }

Object Utility Types

UtilityPurpose
Partial<T>Makes all properties optional
Required<T>Makes all properties required
Readonly<T>Makes all properties readonly
Pick<T, K>Selects specific properties
Omit<T, K>Removes specific properties
Record<K, V>Creates object with key type K

Union Utility Types

UtilityPurpose
Exclude<T, U>Remove types from union
Extract<T, U>Keep only types in union
NonNullable<T>Remove null and undefined

Function Utility Types

UtilityPurpose
ReturnType<T>Get function's return type
Parameters<T>Get function's parameter types
Awaited<T>Unwrap Promise type
Utility types are type-level functions. They take types as input and produce new types as output, enabling powerful type transformations without runtime overhead.
In this exercise, you'll use utility types to transform and manipulate types efficiently, then build your own with mapped types.
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