Here are the top React interview questions to prepare for your next role.
1️⃣ How does React's Virtual DOM improve application performance compared to direct DOM manipulation?
- A) It renders the entire page on the server side before sending it to the client.
- B) It bypasses the browser's rendering engine to draw pixels directly on the screen.
- C) It minimizes direct DOM access by batching changes and updating only modified nodes.
- D) It completely replaces the browser's DOM with a faster JavaScript-based engine.
2️⃣ What is the purpose of 'JSX' in React development?
- A) It is a template engine that compiles HTML files into CSS stylesheets.
- B) It is a rigid strict-type system that prevents runtime errors in JavaScript.
- C) It is a database query language used to fetch data inside React components.
- D) It is a syntax extension that allows writing HTML-like structures within JavaScript.
3️⃣ What is the primary function of the 'useEffect' Hook in a functional component?
- A) It handles the routing logic to navigate between different pages of the app.
- B) It allows performing side effects like data fetching or subscriptions after rendering.
- C) It creates a reference to a DOM element that persists across renders.
- D) It is used to memorize expensive calculations to prevent unnecessary re-renders.
4️⃣ How can 'Component Composition' solve the problem of 'Prop Drilling' without using Context?
- A) By using the spread operator to pass all props automatically down the tree.
- B) By utilizing global variables to store data accessible by any component.
- C) By lifting content up and passing components as 'children' or specific props to layout components.
- D) By creating a Higher-Order Component that injects props into the deeply nested child.
5️⃣ Why does React invoke component render functions twice when running in Strict Mode during development?
- A) To verify that the component can handle receiving two different sets of props.
- B) To ensure that the browser's cache is properly invalidated for assets.
- C) To intentionally stress-test the component and detect side effects in impure render functions.
- D) To simulate the latency of hydration in a Server-Side Rendering environment.