React JS Developer Interview Questions
The world of frontend development has been revolutionized by React.js. This article is tailored to assist hiring professionals in identifying the cream of the React.js developer crop. Through these interview questions, assess both foundational JavaScript skills and in-depth React library knowledge to ensure your web applications are both dynamic and efficient.
What is React?
Answer: React is a JavaScript library developed by Facebook for building user interfaces, primarily for single-page applications.
2.
How does React differ from other frameworks like Angular or Vue?
Answer: React focuses solely on building the UI, whereas frameworks like Angular provide a more comprehensive solution, including routing, HTTP requests, etc. Vue is also focused on the UI but has its own distinct reactive system.
3.
What is JSX?
Answer: JSX stands for JavaScript XML. It allows us to write HTML inside JavaScript and make it work as JavaScript.
4.
How does the Virtual DOM work?
Answer: The Virtual DOM is a representation of the actual DOM. When the state of an object changes, React creates a new Virtual DOM and then compares it with the previous one, updating only the changed parts in the real DOM.
5.
Explain the component lifecycle in React.
Answer: React components have several lifecycle methods, such as componentDidMount, shouldComponentUpdate, and componentWillUnmount, which allow code execution at specific points in a component's lifecycle.
6.
What are controlled components?
Answer: Controlled components are form elements like input, textarea, etc., whose values are controlled by the state. Their value changes are handled by functions.
7.
Describe the significance of keys in React lists.
Answer: Keys help React identify which items in a list have changed, been added, or been removed, thereby optimizing rendering by only updating changed items.
8.
What is Redux?
Answer: Redux is a predictable state container for JavaScript applications. It helps you manage the state of your application in a predictable manner.
9.
Explain the primary components of Redux.
Answer: The three primary components of Redux are Actions, Reducers, and Store.
10.
How is React's context API beneficial?
Answer: The context API allows you to share values (like themes, user authentication) across component boundaries without passing props down manually.
11.
What are hooks in React?
Answer: Hooks are functions that let you use React features like state and lifecycle methods from function components.
12.
Describe the useState and useEffect hooks.
Answer: useState lets you add state to functional components, while useEffect can run side effects after render, akin to lifecycle methods in class components.
13.
How do you optimize the performance of a React application?
Answer: Using techniques like lazy loading, memoization, PureComponent, and preventing unnecessary re-renders can help optimize performance.
14.
What are higher-order components (HOC)?
Answer: HOCs are functions that take a component and return a new component with additional properties or behaviors.
15.
Describe the concept of props in React.
Answer: Props (short for properties) are a way of passing data from parent to child components. They are read-only.
16.
How can you handle form submissions in React?
Answer: Form submissions can be handled by setting the state on every input change and using an event handler like onSubmit to process the form.
17.
What are React fragments?
Answer: Fragments allow you to group a list of children elements without adding extra nodes to the DOM.
18.
How can you integrate TypeScript with React?
Answer: TypeScript can be integrated using Create React App with the TypeScript template or by setting up TypeScript configuration with Webpack and Babel.
19.
Explain the concept of lifting state up in React.
Answer: Lifting state up involves moving shared state to a common ancestor component, ensuring data consistency in child components.
20.
What is prop drilling, and how can it be avoided?
Answer: Prop drilling refers to the process of passing data through multiple levels of components. It can be avoided using context or state management libraries.
21.
How do you handle server-side rendering in React?
Answer: Server-side rendering (SSR) can be achieved using frameworks like Next.js or tools like Rendertron.
22.
How do you handle errors in a React application?
Answer: React 16 introduced error boundaries, which are React components that catch JavaScript errors anywhere in their child component tree.
23.
What's the difference between create-react-app, Next.js, and Gatsby?
Answer: create-react-app is a tool to set up new React projects, Next.js handles SSR and provides a framework for routing, and Gatsby is a static site generator using React.
24.
How do you handle styling in a React app?
Answer: Styling can be handled through traditional CSS, CSS modules, inline styles, or libraries like styled-components.
25.
Describe the flux architecture.
Answer: Flux is a design pattern that ensures consistent data flow through the application. It includes actions, dispatchers, stores, and views.
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