So, you have a new job interview coming up and you want to be well prepared for any questions that may come up for React. Here are some prep questions for you to consider.

General

• What experience do you have with React?
• What projects have used React on?
• What do you think are the pros and cons of React?
• Have you ever experienced any problems while working with React? How did you solve them?
• What do you think makes React better compared to other frontend technologies?
• What is the Virtual DOM, and how does it work?
• What is the difference between an element and a component in React?
• How do you create a simple React component?
• What is the state in React? how is it used?
• What are props in React, and what are they used for?
• What lifecycle methods do React components have?
• What is the difference between controlled and uncontrolled components in React?

What is React?

React is a JavaScript library for building user interfaces and web applications. Its an opensource project created by Facebook that allows developers to create scalable, fast, and simple applications. I like it because it makes it easy to create reusable components that I can use in multiple projects.

What is JSX?

JSX is a syntax extension for JavaScript that allows you to write HTML within your JavaScript code. I enjoy using JSX because it makes my code more readable and easier to understand. It also allows me to use JavaScript and HTML together, making development faster.

Can web browsers read JSX directly?

• Web browsers cannot read JSX directly. This is because they are built to only read regular JS objects and JSX is not a regular JavaScript object.
• For a web browser to read a JSX file, the file needs to be transformed into regular JavaScript and for this React uses Babel.

What are the key features of React?

JSX: JSX is a syntax extension to JavaScript. It is used with React to describe what the user interface should look like. By using JSX, we can write HTML structures in the same file that contains JavaScript code, making the code easy to read and understand. It also makes it easy to write component templates.

Components: Components are the building blocks of any React application, and a single app usually consists of multiple components. It splits the user interface into independent, reusable parts that can be processed separately.

Virtual DOM: Reacts one-way data binding keeps everything modular and fast. A unidirectional data flow means that when designing a React application, you often nest child components within parent components. React uses a virtual DOM to represent the actual DOM. This allows it to update the user interface (UI) efficiently without re-rendering the entire page. It’s component based, so developers can create re-usable components. This facilitates developing complex applications because you can independently update each component. It uses a unidirectional data flow, so it flows in one direction

High Performance: React updates only those components that have changed, rather than updating all the components at once. This results in much faster web applications.

Server Side Rendering: Another feature in which React renders pages on the server, making it quick and easy to load pages. This also ensures the pages are SEO friendly.

What are the components of React?

React components are the building blocks of applications. They are self contained and can be independently updated. Each component has a state which is the data that it uses.

There are two types of components:

• Class Based: Also called stateful components that contain their own state.
• Functional: Also called stateless components, they do not have a state and are functions that return elements

What are the advantages of using React?

React increases efficiency and speeds up the development process. The Virtual DOM improves the performance of applications by only updating the components that have changed instead of re-rendering the entire page. JSX makes it easy to write code and understand the structure of the UI. The component based architecture also eases the development of complex applications. It uses components you can reuse multiple times. You can independently update and reuse these components without affecting the rest of the application.

React uses server side rendering, which makes pages load faster and improves the SEO of an application. This makes it easier for users to find your application. You can easily integrate it with other frameworks such as Next.js, AngularJS, JQuery and Node.js.

What are the potential problems with using React?

React is only a view layer and doesn't provide a full framework. It requires a lot of practice, and it can be challenging to apply it. It uses JSX and inline templating, making the code appear complex and messy for beginners. There are too many components in an application, making it difficult to track them.

What is the Virtual DOM?

The Document Object Model (DOM) represents an HTML document with a logical tree structure. Each branch of the tree ends in a node, and each node contains objects. The virtual document object model represents the actual DOM in memory and is a lightweight representation used by React. When the state of an object changes, the virtual DOM changes only that object in the real DOM, rather than updating all of the objects.

What are controlled and uncontrolled components?

Controlled and uncontrolled components are two different ways of creating forms. You can use controlled components when you want to have complete control over the form and the data entered into it. When you want to allow the user to enter data without having to verify it, you use uncontrolled components. You can use uncontrolled components when you have a simple form that doesn't require much input from the user.

What is the difference between State and Props?

The main difference between state and props is that state is internal to the component and props are external. The state stores data that may change during the lifetime of the component. You can use props to pass data from one component to another. Props are immutable and the component cannot change them, while the component can change the state.