Top questions with answers asked in MNC on React JS

Certainly! Here are three common questions along with sample answers typically asked in MNCs for ReactJS roles:

1. Question: What is ReactJS, and what are its key features? How does it differ from other front-end frameworks like Angular?Answer: ReactJS is an open-source JavaScript library developed by Facebook for building user interfaces, particularly single-page applications (SPAs). Key features of ReactJS include:
   • Component-Based Architecture: ReactJS follows a component-based architecture, where UIs are divided into reusable components. Components encapsulate their own state and behavior, promoting code reusability and maintainability.
   • Virtual DOM: ReactJS uses a virtual DOM (Document Object Model) to represent the UI in memory. Changes to the virtual DOM are efficiently diffed and reconciled with the actual DOM, minimizing DOM manipulation and improving performance.
   • Declarative Syntax: ReactJS employs a declarative syntax, allowing developers to describe the desired UI state, and React takes care of updating the DOM to match that state. This makes it easier to reason about the UI and maintain consistency across components.
   • Unidirectional Data Flow: ReactJS promotes a unidirectional data flow, where data flows downwards from parent components to child components via props. This facilitates predictable state management and simplifies debugging.

   ReactJS differs from other front-end frameworks like Angular in several ways:

   • React is a library, not a full-fledged framework like Angular. It focuses on the view layer of the application and can be used alongside other libraries and frameworks.
   • React’s component-based architecture and virtual DOM make it highly performant and efficient, especially for large-scale applications with complex UIs.
   • React embraces JavaScript’s functional programming features, such as arrow functions and destructuring, whereas Angular relies more on TypeScript and object-oriented programming concepts.
2. Question: What are React hooks, and how do they differ from class components?Answer: React hooks are functions that enable functional components to use state and other React features without writing a class. They were introduced in React 16.8 to address some of the limitations of class components. Here’s how hooks differ from class components:
   • State Management: Hooks allow functional components to use state through the useState hook, whereas class components use the setState method to manage state.
   • Lifecycle Methods: Class components rely on lifecycle methods like componentDidMount and componentDidUpdate to perform side effects and manage component lifecycle. With hooks, functional components can use the useEffect hook to perform side effects in a more declarative and concise manner.
   • Code Reusability: Hooks promote code reusability by allowing logic to be encapsulated and shared across components. Custom hooks enable developers to extract and reuse stateful logic from components without introducing unnecessary nesting or complexity.
   • Readability and Maintainability: Hooks can make functional components more readable and maintainable by removing the need for class boilerplate and simplifying the component’s structure. They encourage a functional programming style and discourage the use of this and class-based syntax.
3. Question: How do you manage state in React applications? What are the different approaches for state management?Answer: State management is a critical aspect of building React applications, especially for managing application state across multiple components. Here are some approaches for state management in React:
   • Local Component State: React components can manage their own state using the useState hook. This approach is suitable for managing component-specific state that doesn’t need to be shared with other components.
   • Context API: React’s Context API allows components to share state across the component tree without passing props explicitly. Context provides a way to pass data through the component tree without having to manually pass props down at every level.
   • Redux: Redux is a predictable state container for JavaScript applications, commonly used with React for managing complex application state. Redux centralizes application state in a single store and provides a set of patterns and tools for managing state updates and data flow.
   • MobX: MobX is another state management library that provides a simpler and more flexible alternative to Redux. MobX uses observable data structures to automatically track state changes and update components accordingly, reducing boilerplate and improving developer productivity.
   • GraphQL: GraphQL is a query language for APIs that enables clients to request and receive only the data they need. GraphQL can be used with React to manage and query application state from a server or external data source, providing a more efficient and declarative approach to data fetching and management.

These answers should provide a solid foundation for tackling ReactJS interview questions in MNCs, showcasing your understanding and expertise in this technology.