JavaScript TypeScript Basics 5

Question 1

What does the non-null assertion operator (`!`) do in TypeScript?

Accepted Answer

Tells the compiler that a value is definitely not null or undefined

Answer

The `!` postfix operator asserts to the compiler that the expression is non-null and non-undefined, suppressing null checks.

Question 2

What is the `unknown` type in TypeScript and how does it differ from `any`?

Accepted Answer

`unknown` requires type narrowing before use, while `any` bypasses type checks entirely

Answer

Unlike `any`, `unknown` forces you to narrow the type before performing operations, making it the type-safe alternative.

Question 3

How do you extend an interface in TypeScript?

Accepted Answer

interface B extends A {}

Answer

TypeScript interfaces use the `extends` keyword to inherit properties from one or more other interfaces.

Question 4

What is a mapped type in TypeScript?

Accepted Answer

A type that transforms each property of an existing type using a template

Answer

Mapped types iterate over the keys of a type and transform each property, enabling reusable type transformations.

Question 5

What does `Record<K, V>` represent in TypeScript?

Accepted Answer

An object type with keys of type K and values of type V

Answer

`Record<K, V>` constructs an object type whose property keys are K and property values are V.

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