Introduction to Intersection and Union Types

Intersection and union types in TypeScript allow you to combine or create flexible types, providing a powerful way to define complex data structures.

What are Union Types?

Union types allow a value to be one of several types. You can define a union type using the | operator.

Example of Union Types

Here’s an example of using a union type:

type Status = 'active' | 'inactive' | 'suspended';

let userStatus: Status;
userStatus = 'active'; // Valid
userStatus = 'pending'; // Error

What are Intersection Types?

Intersection types combine multiple types into one, requiring the combined type to have all properties of the intersected types.

Example of Intersection Types

Here’s an example of using an intersection type:

type User = {
  name: string;
  email: string;
};

type Admin = {
  role: string;
};

type AdminUser = User & Admin;

const admin: AdminUser = {
  name: 'Alice',
  email: 'alice@example.com',
  role: 'admin'
};

Differences Between Union and Intersection Types

Union types allow values to be of multiple possible types, while intersection types combine multiple types into one, requiring all properties to be present.

Practical Use Cases

Union types are great for handling multiple input types, while intersection types are ideal for combining multiple roles or features into one type.

Practice Task

Create a type that combines a Product type with a Discount type using intersection types. Use it to declare a variable.

Congratulations!

You’ve learned how to use union and intersection types to define flexible and combined types in TypeScript. Practice these concepts to make your code more robust and type-safe!