yash's Quiz

What is the correct syntax to define an optional property in an interface?

• property?: type;

• property: type?;

• property: ?type;

• property: Optional<type>;

Which of the following is used to enforce a variable to only have a specific set of values?

• enum

• type

• interface

• const

What will be the result of the following TypeScript code?

let x: number = 10;

let y: string = "Hello";

x = y;

• x will be assigned the value "Hello"

• TypeScript will give a compile-time error because number cannot be assigned a string

• The code will run without error and x will have the value "Hello"

• TypeScript will automatically convert the string to a number

What is the correct way to define a function type that accepts a string and returns a number?

• (x: string) => number;

• (x: string): number => {}

• function(x: string): number;

• type func = (x: string): number;

Which of the following can NOT be a valid type in TypeScript?

• string[]

• Record<string, number>

• string | number

• []string

True or False: Interfaces in TypeScript can merge declarations of the same name within the same scope.

• True

• False

What will be the output of the following TypeScript code?

type User = { name: string; age: number; };

const user: User = {

name: 'Alice',

age: 30,

role: 'Admin', // extra property };

• TypeScript will throw an error because role is not part of User

• TypeScript will throw an error because role is not a string

• user will be valid and role will be added automatically to the User type

• The code will run, but TypeScript will warn about the extra property

Which of the following is a correct use of a Record type?

• type record = Record<string, number>;

• type record = Record<number, string>;

• const record: Record<string, number> = {};

• All of the above

What is the default type for an uninitialized variable in TypeScript?

• any

• unknown

• undefined

• void

What will be the output of this code?

const arr: number[] = [1, 2, 3];

const result = arr.map(x => x * 2);

console.log(result);

• [1, 2, 3]

• [2, 4, 6]

• TypeError: arr.map is not a function

• undefined