React Questions

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Score: 🔥 117

Beginner

Took 6 minutes

Programming Framework

React

70%

Questions Attempted

10 / 10

Correct Answers

Incorrect Answers

Points Earned

🔥 7

Question 1

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 2

What is the primary characteristic of a controlled component in React?

It directly manipulates the DOM to update form values.
It maintains its own internal state for form data.
It relies on the browser to manage form data.
It uses external libraries for form handling.

Explanation:

In React, controlled components store their form data within the component's state. Changes to the form input update the state, and the state updates the input's value, making React the single source of truth.

Question 3

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

MyComponent.defaultProps = { name: 'John' };
defaultProps = { name: 'John' }(MyComponent);
function MyComponent(props) { props.defaultProps = { name: 'John' }; }
export default function MyComponent(props = { name: 'John' }) { }

Explanation:

This syntax correctly assigns an object with default prop values to the 'defaultProps' property of the 'MyComponent' function, providing fallback values for props if not provided.

Question 4

What is the typical approach for handling form submission in React?

Using the browser's default form submission mechanism.
Preventing default behavior and handling submission logic within an event handler.
Submitting the form using AJAX without any event handling.
Using a third-party library to handle all form-related tasks.

Explanation:

In React, it's common to prevent the default form submission behavior. Instead, you attach an onSubmit event handler to the form, which allows you to execute custom logic, like sending data to an API, when the form is submitted.

Question 5

How can you display validation errors to the user in a React form?

By conditionally rendering error messages based on validation results.
By using browser alerts to notify the user of invalid input.
By logging errors to the console for debugging purposes.
By relying solely on HTML5's built-in validation error messages.

Explanation:

A common approach is to conditionally render error messages in your component's JSX. After validating input, you can update the component's state with error information and use it to control the display of error messages.

Question 6

How do you define default props for a functional component in React?

Inside the component's function body
Using the defaultProps property of the component function
By passing them as arguments to the component
Default props are not supported for functional components

Explanation:

You assign an object with default prop values to the defaultProps property of the component function.

Question 7

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 8

How do you pass data from a parent component to a child component in React?

Using state
Using refs
Using props
Using events

Explanation:

Props are a mechanism in React for passing data down the component tree, from parent to child, enabling communication and data flow between components.

Question 9

What will happen if you update the state directly in a class component instead of using this.setState()?

The component will re-render automatically
The state will be updated, but the component won't re-render
An error will be thrown
The application will crash

Explanation:

Directly updating this.state will modify the state, but React won't be aware of this change. this.setState() is crucial as it notifies React about the state update, triggering the necessary re-rendering process.

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.