Reacting to Success: Mastering the 20 Essential Interview Questions for React.js

What is React and what problem does it solve?

• React is a JavaScript library for building user interfaces. It solves the problem of efficiently updating the UI when the underlying data changes.

What are the key features of React?

• Virtual DOM, reusable components, and unidirectional data flow.

What is JSX in React and how does it work?

• JSX is a syntax extension for JavaScript that allows you to write HTML-like code in your JavaScript files. It is transpiled into JavaScript code that React can understand and render.

What is the virtual DOM in React?

• The virtual DOM is a lightweight representation of the actual DOM. React uses it to efficiently update the UI when the underlying data changes.

What is the difference between state and props in React?

• State is internal to a component and can be changed by the component itself, while props are external to a component and are passed down from its parent.

What is a higher-order component (HOC) in React?

• A higher-order component is a function that takes a component and returns a new component with additional functionality.

What is the role of the render() method in React?

• The render() method returns a React element that represents the component's UI.

What is the difference between controlled and uncontrolled components in React?

• Controlled components are those whose state is controlled by React, while uncontrolled components manage their own state.

What is the significance of the key attribute in React?

• The key attribute is used to uniquely identify each component in a list. It helps React efficiently update the UI when the list changes.

What is the difference between pure components and stateful components in React?

• Pure components are those that don't have any internal state of their own and rely entirely on their props, while stateful components manage their own state.

What is Redux and how does it work with React?

• Redux is a state management library for JavaScript applications. It works with React by providing a centralized store that holds the application state.

What is the role of the setState() method in React?

• The setState() method is used to update the state of a component. It triggers a re-render of the component's UI.

What is the significance of the shouldComponentUpdate() method in React?

• The shouldComponentUpdate() method is used to optimize the performance of a React application. It determines whether a component needs to re-render when its props or state change.

What is the difference between React and Angular?

• React is a library for building user interfaces, while Angular is a full-fledged framework for building web applications.

What is the React context API and when should it be used?

• The React context API allows data to be passed down the component tree without having to explicitly pass it through each level. It should be used when data needs to be accessed by multiple components at different levels in the tree.

What is server-side rendering in React and what are its benefits?

• Server-side rendering is the process of rendering a React application on the server, before sending it to the client. Its benefits include improved performance, search engine optimization, and better accessibility.

What is the significance of the useEffect() hook in React?

• The useEffect() hook is used to perform side effects in a React component. It replaces the componentDidMount(), componentDidUpdate(), and componentWillUnmount() lifecycle methods.

What is the difference between React and React Native?

• React is a library for building user interfaces on the web, while React Native is a framework for building native mobile applications.

What is the role of the useRef() hook in React?

• The useRef() hook is used to create a mutable reference that persists across re-renders. It can be used to access DOM elements or to store mutable values that don't trigger a re-render.

What is the significance of the useCallback() hook in React?

• The useCallback() hook is used to memoize functions in a React component. It can help optimize the performance of the component by preventing unnecessary re-renders.

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