React Interview Questions and Answers

Ques 1. What is React?

React is a widely used JavaScript library that was launched in 2011. It was created by developers at Facebook, and it is primarily used for frontend development. React uses the component-based approach, which ensures to help you build components that possess high reusability.

React is well known for developing and designing complex mobile user interfaces and web applications.

Ques 2. What are some of the important features of React?

React has multiple features that are used for unique purposes. The important ones are as mentioned below:

• React makes use of a single-direction data flow model.
• It deals with complete server-side data processing and handling.
• React uses Virtual DOM that has many advantages of its own.

Ques 3. Why is React widely used today?

React provides users with an ample number of advantages when building an application. Some of them are as follows:

• With React, UI testing becomes very easy.
• React can integrate with Angular and other frameworks easily.
• The high readability index ensures easy understanding.
• React can be used for both client-side and server-side requirements.
• It boosts application performance and overall efficiency.
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Ques 4. What is the meaning of the component-based architecture of React?

In React, components are foundations used to build user interfaces for applications. With the component-based system in place, all of the individual entities become completely reusable and independent of each other. This means that rendering the application is easy and not dependent on the other components of the UI.

Ques 5. How does rendering work in React?

Rendering is an important aspect of React as every single component must be rendered. This is done using the render() function. Once the function is called, it returns an element that represents a DOM component.

It is also possible to render more than one HTML element at a time by enclosing the HTML tags and passing them through the render function.

Ques 6. What are states in React?

States form to be one of the vital aspects of React. It is considered as a source of data or objects that control aspects such as component behavior and rendering. In React, states are used to easily create dynamic and interactive components.

Ques 7. What are props in React?

Props are the shorthand name given to properties in React. Props are read-only components that are immutable in nature. In an application, props follow a hierarchy that is passed down from parents to child components. However, the reverse is not supported. This is done to ensure that there is only a single directional flow in data at all times.

Ques 8. What is the use of an arrow function in React?

An arrow function is used to write an expression in React. It allows users to manually bind components easily. The functionality of arrow functions can be very useful when you are working with higher-order functions particularly.

Example: 

MyInput onChange={ (e) => this.handleOnChange(e) }

Ques 9. What is the meaning of create-react-app in React?

The create-react app in React is a simple command-line interface (CLI) that is used in the creation of React applications, which have no build configuration.

All tools are pre-configured when using the CLI, and this allows users to focus on the code more than on dependencies to develop the application.

The following syntax is used to start a simple project in React:

Create-react-app my-app

Ques 10. Why is props passed to the super() function in React?

Props gets passed onto the super() function if a user wishes to access this.props in the constructor.

Ques 11. What is the difference between Virtual DOM and Real DOM?