React Js Practical Interview Questions
Expert-Recommended Practical React JS Interview Questions
React Js practical interview questions are commonly asked to assess a candidate's knowledge and proficiency in the React JavaScript library. These questions aim to evaluate a candidate's practical understanding of various concepts, such as React components, state management, lifecycle methods, and virtual DOM. Interviewers may also ask about common React errors and how to troubleshoot them, best practices for optimizing performance, and techniques for handling application data. These practical questions help employers identify the most qualified and experienced candidates for React development roles.
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1 - What is React?
React is a JavaScript library that is used for building user interfaces. It was created by Facebook and is currently maintained by a community of developers. React allows developers to create complex and dynamic user interfaces efficiently and effectively.
2) What are the main features of React?
Some of the main features of React include the use of reusable components, a virtual DOM for efficient rendering, and the ability to create dynamic user interfaces through its state and props system. React also uses a one-way data flow, allowing for predictable and easy to manage application state.
3) What is JSX?
JSX is a syntax extension for JavaScript that allows developers to write HTML-like code within their JavaScript files. This makes it easier to create and manipulate components in React, as JSX can be compiled down to regular JavaScript code.
4) How does React handle state management?
React uses a concept called “state” to manage and store data within a component. State can be updated using the setState() method, and changes in state will trigger a re-render of the component, ensuring that the interface stays up to date.
5) What is a “Prop” in React?
Props (short for properties) are a way to pass data from a parent component to its child components. They are immutable and can only be passed down from parent to child, ensuring that data flows in a predictable one-way direction.
6) What is the difference between state and props?
The main difference between state and props is that state is managed within a component and can be updated, while props are passed down from a parent component and cannot be changed within the child component.
7) What is a “Component” in React?
A component in React is a reusable piece of code that encapsulates a specific part of the user interface. Components can be composed together to build complex interfaces, and they can also have their own state and props.
8) How does React handle events?
React uses a synthetic event system that wraps native browser events and provides a consistent interface across different browsers. Event handlers are attached to DOM elements using the JSX syntax, and they can be passed down as props to child components.
9) What is the purpose of virtual DOM in React?
The virtual DOM is a representation of the actual DOM, but it lives in memory. When there is a change in state, React compares the virtual DOM with the actual DOM and only updates the necessary DOM elements, making the process more efficient and improving performance.
10) How does React handle routing?
React does not have built-in routing capabilities, but it can be easily integrated with popular libraries like React Router to handle client-side routing.
11) What are Higher-Order Components (HOC) in React?
Higher-Order Components are advanced components that take in another component as an argument and return a new component. They can be used to enhance the functionality of an existing component or to share common logic between multiple components.
12) What is Redux and how is it used in React?
Redux is a popular state management library that can be used in conjunction with React to manage the application state in a centralized location. It follows a unidirectional data flow and can be integrated with React through the use of React-Redux bindings.
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13) What are the advantages of using React?
React offers a number of advantages including better performance due to its virtual DOM, reusable components for easier code maintenance, and a strong and active community for support and resources. It also makes it easier to create complex and dynamic user interfaces.
14) What are some common performance optimization techniques in React?
Some common performance optimization techniques in React include using the shouldComponentUpdate lifecycle method to avoid unnecessary re-renders, implementing lazy loading, and using memoization techniques to prevent unnecessary calculations.
15) What are some tools used for debugging React applications?
Some tools used for debugging React applications include React Developer Tools, Redux DevTools, and the built-in React Profiler tool. These tools allow developers to inspect and debug their applications for any errors or performance issues.
16) How can you improve the SEO of a React application?
To improve the SEO of a React application, it is important to ensure that the application is rendered on the server-side, provide proper meta tags and descriptions, and use tools like React Helmet to manage the document head of the application.
17) What is the purpose of key attribute in React?
The key attribute in React is used to uniquely identify elements in a list of items. It helps React to efficiently re-render the list when there are changes, instead of re-rendering the entire list.
18) How do you handle errors in React?
In React, errors can be handled using the componentDidCatch() lifecycle method, which catches errors in the component and allows for displaying a custom error message. Error boundaries can also be used to handle errors in components and their child components.
19) How can you optimize the performance of a React application?
To optimize the performance of a React application, it is important to ensure that the application follows best practices such as minimizing the use of inline styles, using asynchronous loading techniques, and breaking down large components into smaller ones.
20) What are some popular React libraries?
Some popular React libraries include React Native for building mobile applications, Material-UI for creating UI components, Redux for state management, and Axios for handling API requests.
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