TypeScript TypeScript Type System & Generics

Question 1

What keyword is used to define a generic type parameter in TypeScript?

Accepted Answer

T (angle bracket syntax)

Answer

TypeScript generics use angle bracket syntax (e.g., <T>) to define a type parameter that can be substituted at call or instantiation time.

Question 2

Which TypeScript type represents a value that can be any type and opts out of type checking?

Accepted Answer

any

Answer

The `any` type disables TypeScript's type checking for a variable, allowing it to hold any value without compile-time errors.

Question 3

What is the difference between `unknown` and `any` in TypeScript?

Accepted Answer

`unknown` requires a type check before use; `any` does not

Answer

`unknown` is the type-safe counterpart of `any` — you must narrow it (e.g., with typeof or instanceof) before performing operations on it.

Question 4

Which utility type makes all properties of a type optional?

Accepted Answer

Partial<T>

Answer

`Partial<T>` constructs a type with all properties of T set to optional, meaning each property may or may not be present.

Question 5

What does the `never` type represent in TypeScript?

Accepted Answer

A type with no possible values, such as the return of a function that always throws

Answer

`never` represents the type of values that never occur, commonly used as the return type of functions that always throw or run infinitely.

TypeScript Practice Test