TypeScript Utility Types Reference: All 22 Built-in Types with Examples

#typescript #webdev #javascript #programming

TypeScript ships 22 built-in utility types that transform existing types without re-declaring them. Here is an interactive reference covering all of them — with syntax, examples, TypeScript version requirements, and category filters.

Tool

TypeScript Utility Types Reference
https://devnestio.pages.dev/ts-utility-types/

Features: search by name or description, filter by category (Object / Union / Function / String / Async), copy syntax and examples in one click.

All 22 Types at a Glance

Object Utilities

Type	What it does
`Partial<T>`	Makes all properties optional
`Required<T>`	Makes all properties required
`Readonly<T>`	Makes all properties readonly
`Record<K, V>`	Object type with keys K and values V
`Pick<T, K>`	Subset of T properties
`Omit<T, K>`	T without properties K
`NoInfer<T>`	Prevents inference from a position (TS 5.4+)

Union Utilities

Type	What it does
`Exclude<T, U>`	Remove U members from union T
`Extract<T, U>`	Keep only U members from union T
`NonNullable<T>`	Remove null and undefined from T

Function Utilities

Type	What it does
`ReturnType<T>`	Return type of function T
`Parameters<T>`	Parameter types of function T as tuple
`ConstructorParameters<T>`	Constructor param types as tuple
`InstanceType<T>`	Instance type of constructor T
`ThisParameterType<T>`	The this param type of function T
`OmitThisParameter<T>`	Remove this param from function T
`ThisType<T>`	Mark this context type in object literal

Async

Type	What it does
`Awaited<T>`	Recursively unwrap Promise types (TS 4.5+)

String Utilities (TS 4.1+)

Type	What it does
`Uppercase<S>`	All chars to uppercase
`Lowercase<S>`	All chars to lowercase
`Capitalize<S>`	First char to uppercase
`Uncapitalize<S>`	First char to lowercase

Practical Examples

Partial for update payloads

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

type UserUpdate = Partial<User>;
// { id?: number; name?: string; email?: string; }

async function patchUser(id: number, changes: Partial<User>) { }

ReturnType from factory functions

function createStore() {
  return { count: 0, increment() { this.count++; } };
}

type Store = ReturnType<typeof createStore>;
// { count: number; increment: () => void; }

Awaited to unwrap async types

async function fetchUser(id: number): Promise<User> { }

type FetchResult = Awaited<ReturnType<typeof fetchUser>>;
// User

NoInfer to control inference (TS 5.4+)

function createState<T>(initial: T, fallback: NoInfer<T>): T {
  return initial ?? fallback;
}

createState(42, "hello"); // Error: string not assignable to number

String types for template literals

type Getter<K extends string> = `get${Capitalize<K>}`;
type GetName = Getter<"name">; // "getName"

type EnvKey<K extends string> = `VITE_${Uppercase<K>}`;
type Key = EnvKey<"apiUrl">; // "VITE_APIURL"