Question 1

What are React Hooks? Name a few common ones.

Accepted Answer

**Target Audience:** Anyone preparing for a React interview — assumes components and props. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The hook inventory in section 4 was read directly off the installed React 19.2.8 rather than recalled, which matters because several were added recently. ## 1. Why This Even Matters — A Story First Imagine a workshop where only the master craftsmen were allo

Question 2

How do you handle side effects in functional components?

Accepted Answer

**Target Audience:** Frontend engineers preparing for React interviews — assumes basic familiarity with Hooks. **Difficulty:** Medium > **How to read this doc:** Every concept is explained in plain language first, then tagged with 📌 Interview term: — the exact vocabulary an interviewer expects. Every ordering and lifecycle claim below was produced by actually running React 19.2.8 in a real DOM (jsdom) in this repo, not described from documentation. ## 1. Why This Even Matters — A

Question 3

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 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

Explain the purpose of `useEffect`.

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes useState. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The render counts in section 4 were measured on React 19.2.8. This doc focuses on *when an effect is the wrong tool*; see handling side effects for the broader strategy an

Question 6

What are Error Boundaries in React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — no prior error-handling knowledge assumed. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The behaviour in section 3 was **executed against React 19.2.8**. The companion doc, what an Error Boundary can and cannot catch, covers the limits — which

Question 7

How do you safely handle async work and race conditions inside effects?

Accepted Answer

**Target Audience:** Engineers preparing for senior React interviews — assumes effects and promises. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. This is the deep hazard taxonomy; handling async operations is the introduction, and the race-condition measurement quoted in section 3 comes from there. ## 1. Why This

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