TypeScript TypeScript Classes & Interfaces

Question 1

In TypeScript, what is the key difference between an `interface` and a `type` alias?

Accepted Answer

Interfaces support declaration merging; type aliases do not

Answer

Type aliases support generics; interfaces do not

Answer

Interfaces can only describe objects; type aliases can only describe primitives

Answer

They are completely interchangeable with no differences

Question 2

Which access modifier restricts a class member to be accessible only within the class itself?

Accepted Answer

private

Answer

protected

Answer

public

Answer

readonly

Question 3

What does the `implements` keyword do in a TypeScript class declaration?

Accepted Answer

Declares that the class satisfies the contract of an interface

Answer

Inherits all methods from a parent class

Answer

Creates an abstract base class

Answer

Merges two interfaces into the class

Question 4

What is an abstract class in TypeScript?

Accepted Answer

A class that cannot be instantiated directly and may contain abstract methods

Answer

A class that cannot have any methods

Answer

A class that can be instantiated but not extended

Answer

A class with only static members

Question 5

In TypeScript, what does parameter shorthand in a constructor do?

Accepted Answer

Declares and assigns class properties directly from constructor parameters using access modifiers

Answer

Automatically calls the parent constructor

Answer

Makes all constructor parameters optional

Answer

Prevents the constructor from being overridden

Question 6

What is method overriding in TypeScript classes?

Accepted Answer

Redefining an inherited method in a subclass to change its behavior

Answer

Defining two methods with the same name but different parameter counts

Answer

Making a method private in a subclass

Answer

Calling a method before the class is instantiated