React Interview Masterclass: Top 200 Questions (+PDF) (2026)

Explore React components as reusable building blocks that structure a web page, with header, menu, and footer as examples, and learn the basics: import, functional component, JSX, and export.

Explain how a single page application updates content dynamically on one page without full page reloads, using YouTube as an example.

Explain how arrow function expression in JSX replaces regular function declarations, showing parameters in brackets, arrow operator, and assigning the function to a variable to declare components.

Install NodeJS and a code editor (VS Code), run npx create react app with your project name, then npm start to view your first React project in the browser.

Explore how React delivers reusability and composition through a component-based architecture, enabling component reuse, independent development, and minimal impact when updating parts of an app.

Discover how props in JSX pass data from a parent to a child component, and how to pass parameters and access them as properties like props.name and props.purpose.

Discover how Babel transpiles JSX into JavaScript so browsers understand React code, using the Babel library in node_modules via npm to convert JSX.

Explore the four types of conditional rendering in JSX: if-else, ternary operators, the logical and operator, and switch statements, with guidance on when to use each.

Learn how to iterate over arrays in JSX using the map method, with callback and arrow functions, to double each element and render results efficiently.

Learn how JSX can run without React, using a custom transpiler like Babel, and why this approach is discouraged due to JSX's tight integration with React and its features.

Explore the types of React components, functional and class components, and learn how functional components defined as JavaScript functions or arrow expressions are stateless by default, with hooks enabling state.

Explore five key differences between functional and class components in React, covering syntax, state with hooks versus this.state, lifecycle methods, readability, and the this keyword and render method.

Explore how route parameters in React Router pass dynamic data via the url path to a component, such as a user profile, when a navigation link is clicked.

Explain the useReducer hook for managing complex state with a reducer function and an initial state object, using dispatch and action types, contrast it with useState.

Understand how the useCallback hook memorizes function references in React to prevent unnecessary child rerenders and improve performance, with parent and child examples.

Learn when to use use layout effect to handle DOM elements whose styling depends on external API data, ensuring bold styling only after data arrives, unlike use effect.