FrontEnd Screening Test

1 / 20

What is the key benefit of using Virtual DOM in React?

It enables automatic CSS styling

It speeds up performance by reducing direct DOM manipulation

It directly modifies the real DOM

It allows using different programming languages

2 / 20

What will be the output of `console.log(0.1 + 0.2 === 0.3)`?

NaN

true

undefined

false

3 / 20

What is the purpose of a service worker in a PWA?

To replace JavaScript

A) To manage CSS styling B)C) D)

To handle offline capabilities and caching

To execute server-side logic

4 / 20

What is the difference between `var`, `let`, and `const`?

var cannot be reassigned, let and const can

var is function-scoped, let and const are block-scoped

let is globally available

const can be reassigned

5 / 20

Which of the following will NOT change the original array in JavaScript?

push()

pop()

splice()

map()

6 / 20

What will be the output of `console.log(typeof NaN)`?

NaN

Null

Undefined

Number

7 / 20

In CSS Grid, what does `grid-template-columns: repeat(3, 1fr);` do?

Creates a flexible column layout

Creates 3 columns of equal width

Creates a responsive design

All of the above

8 / 20

What is the purpose of React’s `useState` hook?

To manage global state

To manage component state in function components

To handle API requests

To replace Redux

9 / 20

What is the primary difference between `==` and `===` in JavaScript?

There is no difference

== checks only data type, while === checks only value

== compares values, === compares values and types

=== is faster than ==

10 / 20

In React, which lifecycle method is invoked right after a component is inserted into the DOM?

componentDidMount

componentDidUpdate

componentWillUnmount

shouldComponentUpdate

11 / 20

How do you prevent a default event behavior in JavaScript?

event.cancelEvent()

event.stop()

event.preventDefault()

event.stopPropagation()

12 / 20

Which HTTP status code represents a successful request?

200

302

400

500

13 / 20

In JavaScript, what is the purpose of the `bind()` method?

To bind a function to a specific this context

To modify function parameters

To prevent function execution

To execute a function immediately

14 / 20

What is the purpose of React's `useEffect` hook?

To modify the state

To directly manipulate the DOM

To replace setState

To manage side effects in functional components

15 / 20

Which of the following is NOT a valid JavaScript data type?

Character

Undefined

Symbol

Boolean

16 / 20

What is a closure in JavaScript?

A function that returns another function

A function that is executed immediately

A function that has access to variables from its outer scope

A function with no parameters

17 / 20

What is the difference between `localStorage` and `sessionStorage`?

localStorage persists data even after the browser is closed

Both store data permanently

localStorage can store larger data than sessionStorage

sessionStorage stores data permanently

18 / 20

What is the difference between `.call()` and `.apply()` in JavaScript?

.call() executes a function asynchronously

.call() passes arguments separately, .apply() takes an array of arguments

.apply() is faster than .call()

.apply() is used for defining class components

19 / 20

In CSS, which unit is relative to the width of the viewport?

em

rem

px

vh

20 / 20

Which of the following is a CSS preprocessor?

SCSS

SASS

LESS

All of the above

Your score is

The average score is 57%

0%