Question 1

createContext vs use(Context) — new context consumption in React 19

Accepted Answer

# `createContext` vs. `use(Context)`: New Context Consumption in React 19

**Target Audience:** Frontend engineers preparing for React interviews — assumes basic familiarity with Context and Hooks.
**Difficulty:** Medium

> **How to read this doc:** Every concept is explained in plain language first. Right after, you'll see a callout like `📌 Interview term:` — that's the exact vocabulary a senior engineer would use for the same idea.

## 1. Why This Even Matters — A Story First

Think of Contex

Question 2

What is the purpose of `React.StrictMode`?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes familiarity with useEffect. **Difficulty:** Easy to Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The render and effect counts below were produced by actually mounting components with and without StrictMode on React 19.2.8 in this repo. ## 1. Why This Even Matters — A Story First A flight instructor does not wa

Question 3

How do you manage component-level state without `useState` or `useReducer`?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes hooks basics. **Difficulty:** Easy to Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The class-component behaviour in section 3 was verified by rendering and clicking one on React 19.2.8 — worth checking rather than assuming, given how much has been removed from React 19. ## 1. Why This Even Matters — A Story First A kitchen has a whiteb

Question 4

What are React Components?

Accepted Answer

**Target Audience:** Anyone preparing for a React interview — assumes JavaScript functions, no React required. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The instance and prototype claims in section 4 were produced by inspecting real components on React 19.2.8. ## 1. Why This Even Matters — A Story First Think about LEGO. A brick is small, does one thing, and — crucially — has a standard co

Question 5

When would you choose a class component over a functional component with hooks?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes hooks. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every claim below was **executed against React 19.2.8** — the export check, the hook enumeration, the boundary catching a real error, and the setState merge behaviour. ## 1. Why This Even Matters — A Story First A workshop replaces its hand tools with powe

Question 6

What are Higher-Order Components (HOCs) in React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes components and props. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The losses documented in section 4 were produced by actually building a naive HOC on React 19.2.8 and inspecting what survived. ## 1. Why This Even Matters — A Story First Think of a gift-wrapping service. You hand over a boxed appliance and get back the

Question 7

What is server-side rendering (SSR) and when would you use it with React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — no prior SSR experience assumed. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every server-render output below was **executed against React 19.2.8** using react-dom/server; the raw output is in sections 3 and 5. The companion docs are CSR vs

REACT.JSDECODED.

Easy