Preparing for Your React JS Interview: Must-Know Questions and Tips for Freshers
Written by: Rajat Bhardwaj
If you’re aiming to crack a React JS interview as a fresher, don’t worry! With the right preparation and mindset, you can easily ace it. Here’s a friendly guide packed with essential React JS interview questions, explanations, and tips to help you become a frontend pro. Let’s dive in!
1. What is React JS?
React JS is a popular JavaScript library used for building user interfaces, especially for single-page applications. It’s all about creating interactive and dynamic web experiences. Knowing the basics of React will help you stand out in interviews.
Tip: Understand why React is popular—it’s fast, component-based, and backed by Facebook. Mention these in your interview!
2. What are the Components in React?
Components are the building blocks of a React application. They let you split the UI into independent, reusable pieces. Think of them as the ‘Lego blocks’ of your web page.
Tip: Brush up on functional and class components, and when to use each. Don’t forget Hooks, which are a game-changer!
3. What are Props in React?
Props (short for properties) are like function arguments in JavaScript. They are used to pass data from one component to another.
Example Question: How would you pass data from a parent component to a child component?
Answer: Using props! For example:
function ParentComponent() {
const message = "Hello from Parent!";
return <ChildComponent greeting={message} />;
}
Tip: Remember, props are read-only. You cannot modify them inside a child component!
4. What is State in React?
State is an object that holds data that may change over the lifetime of the component. It’s crucial for creating interactive components.
Example Question: What’s the difference between state and props?
Answer: Props are immutable and passed from parent to child, while state is local and mutable within the component.
Tip: Get comfortable with the useState Hook for managing state in functional components.
5. Explain the Virtual DOM in React.
The Virtual DOM is a lightweight copy of the actual DOM. It allows React to update only the parts of the page that changed, making updates faster.
Example Question: Why is the Virtual DOM faster than the real DOM?
Answer: React compares the virtual DOM with the actual DOM and only updates the necessary parts, reducing the number of changes.
Tip: Use simple language to explain technical terms. Think of the Virtual DOM as a “draft version” of your web page.
6. What is JSX in React?
JSX is a syntax extension that looks like HTML, but it’s used in JavaScript to describe what the UI should look like.
Example Question: Why use JSX instead of plain JavaScript?
Answer: JSX makes the code more readable and easier to write. It’s closer to HTML, so it’s more intuitive for designing UI.
Tip: Don’t worry if JSX feels strange initially—it’s just syntactic sugar over JavaScript!
7. What are Lifecycle Methods in React?
Lifecycle methods are functions that get called at different stages of a component’s life, like mounting, updating, and unmounting.
Example Question: What’s the purpose of componentDidMount?
Answer: It’s used to run code after the component has been rendered, often for fetching data from an API.
Tip: Focus on common methods like componentDidMount, componentDidUpdate, and componentWillUnmount.
8. What is a Hook in React?
Hooks are functions that let you “hook into” React state and lifecycle features in functional components.
Popular Hooks:
useState– for managing state.useEffect– for side effects like data fetching.useContext– for managing global state.
Tip: Practice using Hooks in small projects. They make functional components super powerful!
9. How do you handle forms in React?
Forms are a bit tricky in React because you need to manage their state. You can use controlled or uncontrolled components.
Example Question: What is a controlled component in React?
Answer: A controlled component has its value controlled by React through the state. The form input is updated via a React state handler.
Tip: Learn to handle forms using useState and onChange handlers for smooth user interactions.
10. What is Context API in React?
The Context API allows you to pass data through the component tree without prop drilling. It’s useful for global state management.
Example Question: How do you create a context in React?
Answer: Use React.createContext() and provide it at a higher level in your component tree.
const UserContext = React.createContext();
Tip: Think of the Context API as a way to share “global” data like user info or theme settings.
Bonus Tips for React JS Interview Success:
- Start Small: Begin with basic concepts before moving to advanced topics. It builds confidence!
- Code, Code, Code: Practice coding problems daily. Websites like LeetCode, HackerRank, and FreeCodeCamp are your best friends.
- Projects Speak Louder: Build small projects like a to-do app or a weather app. Showcase them during the interview.
- Stay Calm: Interviews can be nerve-wracking, but remember, it’s just a conversation. Be honest if you don’t know something.
- Ask Questions: If you’re unsure about a question, ask the interviewer to clarify. It shows you’re thoughtful and engaged.
