FrontEnd Screening Test

1 / 20

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

=== is faster than ==

There is no difference

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

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

2 / 20

Which of the following is a CSS preprocessor?

All of the above

LESS

SCSS

SASS

3 / 20

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

componentWillUnmount

shouldComponentUpdate

componentDidMount

componentDidUpdate

4 / 20

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

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

.apply() is faster than .call()

.call() executes a function asynchronously

.apply() is used for defining class components

5 / 20

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

Undefined

Symbol

Boolean

Character

6 / 20

What is a closure in JavaScript?

A function that is executed immediately

A function that has access to variables from its outer scope

A function that returns another function

A function with no parameters

7 / 20

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

localStorage can store larger data than sessionStorage

sessionStorage stores data permanently

Both store data permanently

localStorage persists data even after the browser is closed

8 / 20

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

var cannot be reassigned, let and const can

let is globally available

const can be reassigned

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

9 / 20

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

To replace Redux

To manage component state in function components

To handle API requests

To manage global state

10 / 20

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

px

em

rem

vh

11 / 20

How do you prevent a default event behavior in JavaScript?

event.stopPropagation()

event.cancelEvent()

event.preventDefault()

event.stop()

12 / 20

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

All of the above

Creates 3 columns of equal width

Creates a responsive design

Creates a flexible column layout

13 / 20

Which HTTP status code represents a successful request?

200

302

500

400

14 / 20

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

To execute a function immediately

To modify function parameters

To bind a function to a specific this context

To prevent function execution

15 / 20

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

push()

map()

splice()

pop()

16 / 20

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

It enables automatic CSS styling

It allows using different programming languages

It speeds up performance by reducing direct DOM manipulation

It directly modifies the real DOM

17 / 20

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

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

To replace JavaScript

To handle offline capabilities and caching

To execute server-side logic

18 / 20

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

To manage side effects in functional components

To replace setState

To modify the state

To directly manipulate the DOM

19 / 20

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

Undefined

Number

Null

NaN

20 / 20

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

NaN

undefined

true

false

Your score is

The average score is 57%

0%