20 Virtual DOM Interview Questions and Answers

The Virtual DOM is a popular concept in web development that allows developers to create web applications that are fast, responsive, and scalable. If you’re interviewing for a position that involves working with the Virtual DOM, it’s important to be prepared to answer questions about it. In this article, we’ll discuss some common Virtual DOM interview questions and how you can answer them.

Virtual DOM Interview Questions and Answers

Here are 20 commonly asked Virtual DOM interview questions and answers to prepare you for your interview:

1. What is a Virtual DOM?

A Virtual DOM is a representation of a real DOM. It is a way of abstracting away the actual DOM structure so that developers can work with a simpler, more manageable representation. The Virtual DOM can be used to make changes to the real DOM without having to directly manipulate the DOM itself.

2. Can you explain what ReactJS is?

ReactJS is a JavaScript library that is used for building user interfaces. It is used by Facebook and Instagram, among others. ReactJS allows developers to create reusable components that can be used to create complex UIs.

3. How does the Virtual DOM work in ReactJS?

The Virtual DOM is a JavaScript representation of the actual DOM. It is a way of abstracting away the actual DOM so that React can more efficiently update the UI. When React renders a component, it creates a new Virtual DOM for that component. When the component’s props or state change, React updates the Virtual DOM. Then, when the Virtual DOM has been updated, React updates the actual DOM.

4. Is it possible to create custom components with ReactJS? If yes, then how?

Yes, it is possible to create custom components with ReactJS. In order to do so, you will need to use the createClass method. This method will allow you to create a new component class, which you can then use to create instances of your new component.

5. Can you explain the difference between state and props in ReactJS?

Props are immutable and are passed from the parent component to the child component. State is mutable and is managed within the component.

6. What are the advantages of using Virtual DOM over Real DOM?

The main advantage of using Virtual DOM over Real DOM is that it is much faster and easier to manipulate. With Real DOM, every time you make a change to the DOM, the entire DOM has to be re-rendered. With Virtual DOM, only the part of the DOM that has changed needs to be updated, which is much faster.

7. Why would you use ReactJS for front-end development instead of Angular or VueJS?

ReactJS is a popular front-end development framework because it uses a virtual DOM. This means that when changes are made to the ReactJS component, only the virtual DOM is updated, and not the entire page. This makes ReactJS components more efficient and fast, which is why many developers prefer to use ReactJS for front-end development.

8. What’s the best way to update data in a React application?

The best way to update data in a React application is to use the setState() method. This method will trigger a re-render of the component, which will update the data that is displayed.

9. What’s your understanding of the virtual DOM tree?

The virtual DOM tree is a representation of the actual DOM tree that is used by the browser. It is used to keep track of changes that need to be made to the DOM, and to make those changes in a efficient way.

10. Are there any tools that can be used to track changes made to the DOM?

Yes, there are a few tools that can be used to track changes made to the DOM. The most popular tool is probably the React Developer Tools extension, which can be used to track React components and their associated DOM nodes. There are also a few other tools that can be used to track changes to the DOM, such as the DOM Explorer in Google Chrome.

11. What do you understand about render functions in React applications?

A render function is a function that is used to generate the HTML that will be rendered to the screen for a React component. This function takes in props and state as arguments, and returns a React element.

12. Can you explain what Props are in ReactJS?

Props are a way of passing data from a parent component to a child component. They are immutable, meaning that they cannot be changed by the child component.

13. What is JSX? Can you give me an example of its usage?

JSX is a JavaScript extension that allows for the creation of XML-like structures within JavaScript code. This can be useful for creating reusable components that can be rendered in different ways depending on the context. For example, a component could be rendered as a list item in one context and as a table row in another.

14. Can you explain what lifecycle methods are in ReactJS?

There are a few different lifecycle methods that are called at different points in a component’s life. For example, the componentWillMount method is called before the component is rendered, while the componentDidMount method is called after the component is rendered. Other lifecycle methods include componentWillUpdate, componentDidUpdate, and componentWillUnmount.

15. How do you make sure that child components don’t affect parent data when using ReactJS?

When you are using ReactJS, you need to make sure that you bind the methods to the correct context. This will ensure that the child components do not have access to the parent data.

16. What is a higher order component in ReactJS?

A higher order component is a function that takes a component as an argument and returns a new component that is enhanced with additional functionality. Higher order components are commonly used in React to add additional features to existing components, such as adding a state to a stateless component or adding lifecycle methods to a component.

17. What is Redux? How does it work?

Redux is a JavaScript library for managing application state. It works by providing a central store that holds the state of the entire application. When a component needs to update its state, it dispatches an action to the store. The store then updates its state based on the action, and the new state is propagated to all of the components. This ensures that all of the components always have the same, up-to-date state.

18. What is Flux? How does it compare to Redux?

Flux is a JavaScript library for managing application data flow. It is similar to Redux in that it uses a unidirectional data flow model, but it differs in that it does not have a centralized store. Instead, Flux uses a dispatcher to broadcast actions to all of the registered stores. This can make debugging Flux applications more difficult than Redux applications, but it also allows for more flexibility in how data is managed.

19. How does ReactJS handle immutability?

ReactJS uses a virtual DOM to keep track of changes to the state of a component. When a component’s state is changed, ReactJS will update the virtual DOM accordingly. When the virtual DOM is updated, ReactJS will then compare the virtual DOM to the actual DOM and make the necessary changes to the actual DOM. This process ensures that the actual DOM is always in sync with the virtual DOM, and that changes to a component’s state are always reflected in the actual DOM.

20. What is the difference between immutable and mutable objects?

Immutable objects are those that cannot be changed after they are created. Mutable objects, on the other hand, can be changed after they are created. Virtual DOM objects are typically immutable, which means that they can be more efficiently updated and manipulated by the browser.