What are Intersection Types in TypeScript?

Combining multiple types into one.

What You'll Learn

What intersection types are
How to combine types
Use cases

Intersection Types

An intersection type combines multiple types into one using the & operator. The result has all properties from all types.

code.tsTypeScript

type Person = {
  name: string;
  age: number;
};

type Employee = {
  employeeId: string;
  department: string;
};

// Intersection: has all properties
type Staff = Person & Employee;

const staff: Staff = {
  name: "John",
  age: 30,
  employeeId: "E123",
  department: "Engineering"
};

Extending Interfaces

code.tsTypeScript

interface Printable {
  print(): void;
}

interface Loggable {
  log(): void;
}

type Document = Printable & Loggable;

const doc: Document = {
  print() { console.log("Printing..."); },
  log() { console.log("Logging..."); }
};

Use Cases

Mixing in behaviors
Combining configurations
Creating complex object shapes

What are Union Types in TypeScript?

What is Type Assertion in TypeScript?