Basic Questions
1) What is React?
React is a JavaScript library developed by Facebook for building user interfaces, particularly single-page applications (SPAs). It allows developers to create reusable UI components that manage their own state, making it easier to build complex user interfaces in a modular and maintainable way.
2) What are components in React?
In React, components are the building blocks of the user interface. They encapsulate a piece of the UI, allowing you to create reusable, self-contained units that manage their own state and behavior. Components can be thought of as custom HTML elements that can accept inputs (called “props”) and maintain their own state.
3) What is JSX?
JSX, or JavaScript XML, is a syntax extension for JavaScript commonly used with React. It allows developers to write HTML-like code directly within their JavaScript files. JSX makes it easier to visualize the structure of the UI and is one of the key features that contribute to React’s declarative approach to building user interfaces.
4) What is the difference between state and props?
Intermediate Questions
5) What are hooks in React?
Hooks are a feature introduced in React 16.8 that allow developers to use state and lifecycle methods in functional components. They provide a more straightforward and expressive way to manage state and side effects, promoting cleaner and more reusable code. Hooks eliminate the need for class components in many cases, making functional components more powerful.
6) Types of hooks in React?
7) What is the context API?
The Context API is a feature in React that provides a way to share values (such as state) between components without having to pass props down manually through every level of the component tree. This is particularly useful for global data that needs to be accessed by multiple components, such as user authentication, theme settings, or application settings.
8) What is React Router?
React Router is a powerful library for routing in React applications, enabling the navigation between different components, views, or pages without reloading the entire application. It allows developers to create single-page applications (SPAs) with a smooth user experience by managing the routing and rendering of components based on the URL.
Advanced Questions
9) What are higher-order components (HOCs) in React?
10) What is Redux, and how does it work with React?
Redux is a predictable state management library for JavaScript applications, commonly used with React to manage the application’s state in a centralized manner. It provides a way to maintain a consistent state across an application, making it easier to reason about data flow and manage complex state interactions.
11) How do you optimize performance in a React application?
Scenario-Based Questions
12) How do you optimize performance in a React application?
To optimize performance in a React application, key strategies include: using React.memo for memoization to avoid unnecessary re-renders, implementing lazy loading to load components only when needed, utilizing React.Suspense for loading states, leveraging server-side rendering (SSR) for faster initial page load, optimizing list rendering with proper keys, avoiding unnecessary state updates, and profiling your application to identify performance bottlenecks.
13) How do you approach testing in React?
Testing in React is essential for ensuring that your components behave as expected, are free of bugs, and maintain their functionality as your application evolves. Here’s an overview of how to approach testing in React:
Testing in React is crucial for building robust and reliable applications. Here’s a comprehensive approach to testing React components:
14) Can you explain the concept of "lifting state up"?
“Lifting state up” is a concept in React that involves moving state management to a higher-level component when multiple components need access to the same piece of state. This approach helps ensure that state is consistent and centralized, making it easier to manage and reason about.
“Lifting state up” in React refers to the practice of moving state data from a child component to a parent component (the closest common ancestor) when multiple child components need to share and update the same data, ensuring a single source of truth for that data across the component hierarchy and maintaining consistency in the UI when changes occur; essentially, the parent component manages the state and passes it down to its children as props, allowing them to access and update the shared data as needed
15) What is the difference between controlled and uncontrolled components?
