Question 1

What is `PropTypes` and when would you use it?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes basic component knowledge. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. This topic has a genuine breaking change behind it, so the central claim below was verified by actually rendering a component with propTypes on React 19.2.8 and by checking the React upgrade guide — not recalled. ## 1. Why This Even Matter

Question 2

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 3

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 4

Describe the React component lifecycle.

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes hooks basics. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every ordering below is **executed output from React 19.2.8**, not a description — the raw sequences are in sections 3 and 5. ## 1. Why This Even Matters — A Story First A market stall has three moments: setting up before opening, adjusting through the day as st

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

REACT.JSDECODED.

Easy

What is `PropTypes` and when would you use it?

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

What are React Components?

Medium

Describe the React component lifecycle.

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