TypeScript TypeScript Classes & Interfaces 2

Question 1

What are TypeScript decorators primarily used for?

Accepted Answer

Applying metadata or modifying the behavior of classes, methods, and properties at design time

Answer

Decorators are special declarations (prefixed with `@`) that can attach metadata or wrap the behavior of a class, method, accessor, property, or parameter.

Question 2

What does `readonly` do when applied to a class property?

Accepted Answer

Prevents the property from being reassigned after initialization

Answer

`readonly` properties can only be assigned during declaration or in the constructor; any attempt to reassign them later causes a compile-time error.

Question 3

Which TypeScript feature allows a class to have multiple method signatures?

Accepted Answer

Function overloads

Answer

Function (or method) overloads let you define multiple type signatures for the same function, with a single implementation that handles all the cases.

Question 4

What is the `protected` access modifier in TypeScript?

Accepted Answer

Accessible within the declaring class and all subclasses

Answer

`protected` members are accessible within the declaring class and any class that extends it, but not from outside the class hierarchy.

Question 5

In TypeScript, what does interface extending multiple interfaces achieve?

Accepted Answer

It creates an interface that combines all properties from every extended interface

Answer

An interface can extend multiple interfaces (e.g., `interface C extends A, B`), inheriting all their members into one combined contract.

TypeScript Practice Test

TypeScript Practice Test

TypeScript TypeScript Classes & Interfaces 2