Interview Prep

React100: UI Architecture

Master React from components and hooks to complex state management and performance optimization with the 'UI as a function of state' philosophy.

Total Questions

100

Core Concepts

Architecture

Modern Hooks

Functional

Performance

Optimization

Core Concepts

8 questions

Component Lifecycle (Deep Dive)

6 questions

useEffect & The Dependency Array (Deep Dive)

8 questions

All Hooks — Deep Dive

12 questions

State Management

5 questions

Rendering & Reconciliation

6 questions

Events, Forms & User Interaction

4 questions

Component Patterns & Composition

6 questions

Routing

3 questions

Data Fetching & Side Effects

3 questions

Performance Optimization

4 questions

Advanced Topics & Ecosystem

35 questions

Previous: JavaScript Next: Node.js

React100: UI Architecture

Core Concepts

What is React and why do developers use it?

What is JSX and how is it different from HTML?

What is the Virtual DOM and how does React use it?

What is a React component?

What are props and how do they work?

What is state and how is it different from props?

What is one-way data flow (unidirectional data flow)?

What is re-rendering in React?

Component Lifecycle (Deep Dive)

What are the three phases of a React component's lifecycle?

What happens at the Mount phase?

What happens at the Update phase?

What happens at the Unmount phase?

What is the exact order of lifecycle events in a React functional component?

How do class component lifecycle methods map to hooks?

useEffect & The Dependency Array (Deep Dive)

What does useEffect do?

What is the dependency array in useEffect?

How does React compare dependency array values?

What causes an infinite loop in useEffect?

What should and should NOT go in the dependency array?

What is the cleanup function in useEffect and why is it important?

Why does useEffect run twice in development (React 18 StrictMode)?

What is the difference between useEffect and useLayoutEffect?

All Hooks — Deep Dive

What are the rules of Hooks?

How does useState work in detail?

What is a stale closure in React hooks?

What does useRef do and when should you use it?

What is useContext and how does the Context API work?

What does useMemo do and when should you use it?

What does useCallback do and how is it different from useMemo?

What does useReducer do and when should you use it over useState?

What are custom hooks and how do you build one?

What does useId do?

What does useTransition do?

What does useDeferredValue do?

State Management

What is the lifting state up?

What is prop drilling and how do you solve it?

What is state batching and how does it work in React 18?

What is the difference between controlled and uncontrolled components?

What is Zustand and how does it compare to Context?

Rendering & Reconciliation

What is reconciliation?

Why is the key prop important in lists?

What is React Fiber?

What is React.memo and how does it prevent unnecessary re-renders?

What is the key trick for resetting component state?

What is lazy loading and code splitting in React?

Events, Forms & User Interaction

How do events work in React (synthetic events)?

How do you handle forms in React?

What is event bubbling and how do you stop it?

How do you debounce user input in React?

Component Patterns & Composition

What is component composition and why is it preferred over inheritance?

What are Higher-Order Components (HOC)?

What are Error Boundaries?

What is a React Portal and when do you need one?

What is forwardRef and why is it needed?

What is the Compound Component pattern?

Routing

What is React Router and how do you use it?

What is the difference between client-side and server-side routing?

How do you protect routes (authentication-based routing)?

Data Fetching & Side Effects

How do you fetch data in React properly?

What is React Query (TanStack Query) and why use it?

What is the race condition problem in data fetching?

Performance Optimization

What causes unnecessary re-renders?

How do you profile and find performance issues in React?

What is Concurrent React and what problems does it solve?

What is React's automatic batching (React 18)?

Advanced Topics & Ecosystem

What is SSR (Server-Side Rendering) and how does React support it?

What are React Server Components (RSC)?