100% Free
🎯 3200+ Questions. One Goal: Your Success Sign In Sign Up

Entry React Interview Questions

Curated Entry-level React interview questions for developers targeting entry positions. 20 questions available.

Last updated:

React Interview Questions & Answers

Skip to Questions

Welcome to our comprehensive collection of React interview questions and answers. This page contains expertly curated interview questions covering all aspects of React, from fundamental concepts to advanced topics. Whether you're preparing for an entry-level position or a senior role, you'll find questions tailored to your experience level.

Our React interview questions are designed to help you:

  • Understand core concepts and best practices in React
  • Prepare for technical interviews at all experience levels
  • Master both theoretical knowledge and practical application
  • Build confidence for your next React interview

Each question includes detailed answers and explanations to help you understand not just what the answer is, but why it's correct. We cover topics ranging from basic React concepts to advanced scenarios that you might encounter in senior-level interviews.

Use the filters below to find questions by difficulty level (Entry, Junior, Mid, Senior, Expert) or focus specifically on code challenges. Each question is carefully crafted to reflect real-world interview scenarios you'll encounter at top tech companies, startups, and MNCs.

Questions

20 questions
Q1:

What problem does React solve compared to directly manipulating the DOM?

Entry

Answer

React uses a virtual DOM to batch updates and apply only necessary changes to the real DOM. This reduces reflow and repaint costs, making UI updates efficient and predictable.
Permalink
Q2:

What is JSX and why do we use it in React?

Entry

Answer

JSX is a JavaScript syntax extension that allows writing HTML-like code within JavaScript. It improves readability and compiles into React.createElement() calls during build.
Permalink
Q3:

Why must React components start with a capital letter?

Entry

Answer

React treats lowercase tags as built-in HTML elements. Uppercase names indicate custom components so React can instantiate them correctly.
Permalink
Q4:

What is the purpose of the createRoot API introduced in React 18?

Entry

Answer

createRoot enables concurrent rendering, allowing React to pause, resume, or interrupt rendering to improve UI responsiveness.
Permalink
Q5:

What is the difference between a Component and an Element in React?

Entry

Answer

A component is a function or class defining UI logic. An element is the object returned by that component describing what to render.
Permalink
Q6:

What is the use of React Fragment?

Entry

Answer

Fragments (<> ) let you return multiple elements without adding extra DOM nodes, keeping layouts cleaner.
Permalink
Q7:

Why do we use keys in lists?

Entry

Answer

Keys help React track which list items changed, were added, or removed, enabling efficient virtual DOM reconciliation.
Permalink
Q8:

What happens if we use the array index as a key?

Entry

Answer

Using array indexes can cause React to reuse incorrect DOM nodes, leading to bugs like wrong input values or lost component state during reorder.
Permalink
Q9:

What is the difference between props and state?

Entry

Answer

Props are read-only inputs passed from parent components, while state is internal mutable data managed by the component.
Permalink
Q10:

Can a component modify its own props?

Entry

Answer

No. Props are immutable and controlled by the parent. Changing them breaks unidirectional data flow.
Permalink
Q11:

What does useState() return?

Entry

Answer

useState returns an array with the current state value and a function to update that state.
Permalink
Q12:

Why doesn’t updating state directly trigger a re-render?

Entry

Answer

React re-renders only when the state updater function is called. Direct mutation does not notify React.
Permalink
Q13:

What is the purpose of useEffect?

Entry

Answer

useEffect runs side effects after rendering, such as API calls, subscriptions, timers, or DOM manipulation.
Permalink
Q14:

What happens if you forget dependencies in useEffect?

Entry

Answer

The effect runs after every render, potentially causing infinite loops or unnecessary API requests.
Permalink
Q15:

What is controlled vs uncontrolled component in forms?

Entry

Answer

Controlled components store form values in React state. Uncontrolled components store input values in the DOM and use refs to access them.
Permalink
Q16:

What is React Strict Mode and why is it useful?

Entry

Answer

Strict Mode highlights potential issues by intentionally double-running certain logic in development to detect unsafe patterns.
Permalink
Q17:

What is Concurrent Rendering in React 18?

Entry

Answer

Concurrent Rendering allows React to pause, resume, interrupt, and prioritize UI rendering tasks for better responsiveness.
Permalink
Q18:

What is useId introduced in React 18?

Entry

Answer

useId generates unique, stable IDs used for accessibility attributes and prevents hydration mismatches in SSR.
Permalink
Q19:

What is the difference between useEffect and useLayoutEffect?

Entry

Answer

useEffect runs after the browser paints. useLayoutEffect runs before paint and is used for layout measurements.
Permalink
Q20:

What are React Server Components?

Entry

Answer

Server Components run on the server, fetch data directly, and send lightweight results to the client, reducing bundle size and improving performance.
Permalink

Curated Sets for React

No curated sets yet. Group questions into collections from the admin panel to feature them here.

People Also Ask - Related React Questions

What problem does React solve compared to directly manipulating the DOM?
What is JSX and why do we use it in React?
Why must React components start with a capital letter?
What is the purpose of the createRoot API introduced in React 18?
What is the difference between a Component and an Element in React?
What is the use of React Fragment?
Ready to level up? Start Practice