React Questions

Ritik Yadav

Score: 🔥 35

Beginner

Took 12 minutes

Programming Framework

React

90%

Questions Attempted

10 / 10

Correct Answers

Incorrect Answers

Points Earned

🔥 9

Question 1

What is a key advantage of using a controlled component for a file input in React?

Direct access to the file data in the component's state.
Simplified styling of the file input element.
Automatic upload of the file to the server.
Improved browser compatibility for file uploads.

Explanation:

With a controlled file input, the selected file data is stored within your component's state, giving you more control over handling, previewing, and uploading the file.

Question 2

Which of the following JSX expressions is INVALID?

<h1>Hello, {name}!</h1>
<div id={'container'}></div>
<p>2 + 2 = {2 + 2}</p>
<span>This is incorrect {</span>

Explanation:

JSX expressions must be valid JavaScript. You cannot have an opening curly brace '{' without a corresponding closing brace '}' within a JSX expression.

Question 3

What is the purpose of form validation in React?

To style form elements based on user input.
To ensure data integrity and prevent invalid submissions.
To automatically submit the form when all fields are filled.
To send data to the server for validation.

Explanation:

Form validation is crucial for maintaining data quality. It involves checking if the user's input meets predefined criteria (e.g., required fields, email format) before it's submitted.

Question 4

How does the useEffect Hook in functional components relate to lifecycle methods in class components?

useEffect is a replacement for componentDidMount only.
useEffect combines the functionality of componentDidMount, componentDidUpdate, and componentWillUnmount.
useEffect is only used for data fetching.
There is no relationship between useEffect and lifecycle methods.

Explanation:

The useEffect Hook allows you to perform side effects within functional components. By specifying dependencies, it can mimic the behavior of componentDidMount (no dependencies), componentDidUpdate (dependencies), and componentWillUnmount (return a cleanup function).

Question 5

What happens if a prop is not provided to a component with a default prop defined?

An error is thrown
The component will not render
The default prop value is used
The prop will be undefined

Explanation:

Default props act as fallback values when a prop is not explicitly passed to the component.

Question 6

How do uncontrolled components in React handle form data?

By using refs to directly access and manage DOM values.
By storing the data in a global state management library.
By relying on data binding between the form and component state.
By sending an HTTP request to the server on every input change.

Explanation:

Uncontrolled components in React don't rely on the component's state for form data. Instead, they use refs to directly interact with the DOM, allowing you to extract values when needed.

Question 7

What are Synthetic Events in React?

Native browser events directly exposed by the DOM
React's custom event objects that wrap native events
Events triggered only by synthetic user actions (like bot interactions)
Events related to state changes within a React component

Explanation:

Synthetic events are plain JavaScript objects created by React that hold information about an event across different browsers. They provide a consistent API and prevent cross-browser inconsistencies.

Question 8

Which of the following is a key benefit of using controlled components in React forms?

Direct manipulation of the DOM for improved performance.
Simplified state management with reduced boilerplate code.
Enhanced control over form data and validation.
Seamless integration with external libraries for form handling.

Explanation:

Controlled components excel at providing granular control over form data. By storing data in React's state, you can easily implement validation, dynamic updates, and custom form logic.

Question 9

What is the correct syntax for a functional component in React?

class Welcome extends React.Component { ... }
function Welcome(props) { ... }
const Welcome = () => { ... };
let Welcome = (props) => { ... }

Explanation:

This is the most common and recommended syntax for defining functional components in modern React, using arrow functions.

Question 10

What is the purpose of PropTypes in React?

To enforce the data type of props
To style components
To manage component state
To handle user events

Explanation:

PropTypes help ensure that components receive the correct data type for their props, improving code reliability.