How do I extend interfaces in TypeScript?

How do I extend interfaces in TypeScript?

In TypeScript, you can extend interfaces using the extends keyword. For example, if you have an interface A, you can create a new interface B that extends A like this: interface B extends A { ... }.

Can you give me an example of extending an interface?

Sure! Here's a simple example:

interface Person {
  name: string;
  age: number;
}

interface Employee extends Person {
  employeeId: number;
}

In this case, Employee has all properties of Person plus an additional employeeId.

What if I want to add methods to the extended interface?

You can add methods in the same way you add properties. For example:

interface Employee extends Person {
  employeeId: number;
  getDetails(): string;
}

Now, Employee has a method getDetails in addition to its properties.

Can I extend multiple interfaces?

Yes, you can extend multiple interfaces by separating them with commas. For example:

interface Manager extends Employee, Person {
  department: string;
}