Introducing TypeScript

Question 1

Why can’t TypeScript run directly in a browser?

Answer 1

It must be transpiled into JavaScript first.

Question 2

What is the main benefit of TypeScript over JavaScript?

Answer 2

It adds a rich type system to JavaScript.

Question 3

What is the purpose of the unknown type in TypeScript?

Answer 3

It is used when the type is uncertain but requires type safety.

Question 4

What must be done before using a variable of type unknown?

Answer 4

It must be explicitly checked before use.

Question 5

What is a type predicate in TypeScript?

Answer 5

A function that verifies a value’s type.

Question 6

How do you define a custom type in TypeScript?

Answer 6

Using the type keyword.

Question 7

What operator is used to extend types in TypeScript?

Answer 7

The & (intersection) operator.

Question 7

How do you define a type alias for a product with an optional price in TypeScript?

Answer 7

type Product = { name: string; unitPrice?: number };

Question 8

How do you create a DiscountedProduct type that extends Product?

Answer 8

type DiscountedProduct = Product & { discount: number };

Question 9

What does the following TypeScript snippet do?

fetch("https://swapi.dev/api/people/1")
  .then((response) => response.json())
  .then((data: unknown) => {
    if (isCharacter(data)) {
      console.log("name", data.name);
    }
  });

Answer 9

It fetches data from an API, ensures type safety by using unknown, and checks the type before accessing properties.