ReactJS fresher interview questions with answers

 Here are some ReactJS fresher interview questions with answers:

1. What is React?

React is a JavaScript library for building user interfaces. It is used to create interactive web applications. React is based on the concept of components, which are small, reusable pieces of code that can be combined to create complex UIs.

2. What are the benefits of using React?

There are many benefits to using React, including:

• Performance: React uses a virtual DOM, which allows it to update the UI only when necessary. This can lead to significant performance improvements over traditional approaches to UI development.
• Scalability: React is very scalable, and can be used to build large, complex applications.
• Community: React has a large and active community, which means there are many resources available to help developers learn and use React.

3. What are the limitations of using React?

There are a few limitations to using React, including:

• Learning curve: React can have a steep learning curve, especially for developers who are new to JavaScript.
• Dependencies: React has a number of dependencies, which can make it difficult to set up and use.
• Not a complete framework: React is a library, not a framework. This means that it does not provide everything that is needed to build a complete web application.

4. What is JSX?

JSX is a syntax extension for JavaScript that allows developers to write HTML-like code in JavaScript files. JSX is used to create React components.

5. What is the virtual DOM?

The virtual DOM is a representation of the UI that is stored in memory. When the state of a component changes, React compares the new state to the old state and only updates the parts of the UI that need to be updated. This can lead to significant performance improvements over traditional approaches to UI development.

6. What are props?

Props are arguments that are passed to a component. Props can be used to pass data into a component or to control the behavior of a component.

7. What is the state?

The state is the data that is stored inside a component. The state can be used to keep track of the current state of a component, such as the user's input or the current selection.

8. What are the different phases of the component lifecycle?

The component lifecycle is a series of events that occur when a component is created, updated, or destroyed. The different phases of the component lifecycle are:

• Mounting: This is the phase when a component is created and added to the DOM.
• Updating: This is the phase when a component is updated.
• Unmounting: This is the phase when a component is removed from the DOM.

9. What are the different ways to style a React component?

There are a few different ways to style a React component, including:

• Using CSS: CSS can be used to style React components. CSS can be applied to individual components or to the entire application.
• Using inline styles: Inline styles can be used to style React components. Inline styles are written directly inside the component markup.
• Using CSS modules: CSS modules are a way to scope CSS to individual components. CSS modules can be used to prevent CSS conflicts between different components.
• Using styled-components: styled-components is a library that makes it easy to create styled React components. styled-components provides a number of features that make it easier to write and maintain CSS for React components.

10. What are some tips for writing efficient React code?

Here are a few tips for writing efficient React code:

• Use the virtual DOM: The virtual DOM can help to improve the performance of React applications by only updating the parts of the UI that need to be updated.
• Use functional components: Functional components are more efficient than class components. Functional components do not have a lifecycle, which can improve performance.
• Use memoization: Memoization can be used to cache the results of expensive calculations. This can improve performance by avoiding the need to recalculate the results of expensive calculations every time they are needed.
• Use lazy loading: Lazy loading can be used to load components only when they are needed. This can improve performance by avoiding the need to load components that are not needed.

These are just a few of the ReactJS fresher interview questions that you may be asked. By preparing for these questions, you can increase your chances of success in your next ReactJS interview.