Utility Types: Learn TypeScript’s built-in utility types like Partial, Pick, Omit, and Record

TypeScript provides a set of utility types that help manipulate types in various ways, making it easier to write flexible and reusable code.

Let's explore some of the most commonly used utility types: Partial, Pick, Omit, and Record.

1. Partial<T>

Description: Constructs a type with all the properties of T set to optional.
Use case: When you want to create a version of an object type where all fields are optional.

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

const updateUser = (user: Partial<User>) => {
  // Now all properties of User are optional.
  console.log(user);
};

updateUser({ name: 'John' }); // Valid
updateUser({});              // Valid

2. Pick<T, K>

Description: Constructs a type by picking a set of properties K from T.
Use case: When you want to create a new type with a subset of properties from an existing type.

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

type UserPreview = Pick<User, 'id' | 'name'>;

const user: UserPreview = {
  id: 1,
  name: 'John',
};

console.log(user); // Only `id` and `name` are required.

3. Omit<T, K>

Description: Constructs a type by omitting a set of properties K from T.
Use case: When you want to exclude certain properties from an existing type.

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

type UserWithoutEmail = Omit<User, 'email'>;

const user: UserWithoutEmail = {
  id: 1,
  name: 'John',
};

console.log(user); // Only `id` and `name` are required.

4. Record<K, T>

Description: Constructs a type with a set of properties K of type T.
Use case: When you want to map a set of keys to a specific type.

type Role = 'admin' | 'editor' | 'viewer';

const roles: Record<Role, boolean> = {
  admin: true,
  editor: false,
  viewer: true,
};

console.log(roles); // Each role maps to a boolean value.

Summary Table:

Utility Type	Purpose	Example Use Case
Partial	Makes all properties optional in a given type.	Updating objects with optional fields.
Pick	Selects a subset of properties from a type.	Creating a minimal type for previews.
Omit	Excludes a subset of properties from a type.	Removing sensitive fields from an API response.
Record	Maps a set of keys to a specified type.	Creating objects with fixed keys and specific types.

Typescript Conditional Types: Use extends, infer, and keyof to create conditional logic in types.

Javascript working with arrays of objects