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.

1interface User {
2  id: number;
3  name: string;
4  email: string;
5}
6
7const updateUser = (user: Partial<User>) => {
8  // Now all properties of User are optional.
9  console.log(user);
10};
11
12updateUser({ name: 'John' }); // Valid
13updateUser({});              // Valid
14

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.

1interface User {
2  id: number;
3  name: string;
4  email: string;
5}
6
7type UserPreview = Pick<User, 'id' | 'name'>;
8
9const user: UserPreview = {
10  id: 1,
11  name: 'John',
12};
13
14console.log(user); // Only `id` and `name` are required.
15

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.

1interface User {
2  id: number;
3  name: string;
4  email: string;
5}
6
7type UserWithoutEmail = Omit<User, 'email'>;
8
9const user: UserWithoutEmail = {
10  id: 1,
11  name: 'John',
12};
13
14console.log(user); // Only `id` and `name` are required.
15

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.

1type Role = 'admin' | 'editor' | 'viewer';
2
3const roles: Record<Role, boolean> = {
4  admin: true,
5  editor: false,
6  viewer: true,
7};
8
9console.log(roles); // Each role maps to a boolean value.
10

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