Question 1

What are React synthetic events?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — no prior knowledge of the event system assumed. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Everything about the event object below was **executed against React 19.2.8** and the raw output is pasted in section 3. For the delivery mechanism — where the listener actually lives — see

Question 2

What is the role of `react-dom`?

Accepted Answer

**Target Audience:** Frontend engineers preparing for React interviews — assumes basic familiarity with components. **Difficulty:** Easy to Medium > **How to read this doc:** Every concept is explained in plain language first. Right after, you will see a callout like 📌 Interview term: — that is the exact vocabulary a senior engineer would use for the same idea. Every package-export and behavioural claim below was produced by actually running React 19.2.8 in this repo, not describe

Question 3

Explain the concept of 'unidirectional data flow' in React.

Accepted Answer

**Target Audience:** Anyone preparing for a React interview — assumes props and state. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The prop-mutation result in section 4 was produced by actually assigning to a prop on React 19.2.8 and catching what happened. ## 1. Why This Even Matters — A Story First A newspaper has one editor per section. Reporters file copy upward; the editor decides what

Question 4

What is the difference between element and component in React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes basic JSX familiarity. **Difficulty:** Easy to Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every object-shape claim below was produced by inspecting real values in React 19.2.8, not described from documentation. ## 1. Why This Even Matters — A Story First A **recipe** for a cake is not a cake. It is also not an *order* for a cake. -

Question 5

What are React's design principles?

Accepted Answer

**Target Audience:** Engineers preparing for senior React interviews — assumes broad familiarity with the API. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. This is a discussion question rather than a mechanical one, so instead of a "Verified" section it cites the React team own published principles and ties each to a concrete API you already use. ## 1. Why This Even Matters — A Story First

Question 6

How would you structure a large React application?

Accepted Answer

**Target Audience:** Engineers preparing for senior React interviews — assumes practical experience. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** this is an architecture question with no runtime behaviour to measure, so nothing here was executed and none of it is presented as measured. Where a claim rests on something measurable elsewhere in this collection, it lin

Question 7

What is the difference between shadow DOM and virtual DOM?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — no prior Web Components knowledge assumed. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The object shapes and the encapsulation test in section 3 were **executed against React 19.2.8** in a real DOM. Related: the virtual DOM in depth and

Question 8

How does React Fiber work?

Accepted Answer

**Target Audience:** Engineers preparing for senior React interviews — assumes reconciliation basics. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Sections 3 and 5 are **actual fiber nodes read out of a running React 19.2.8 tree** — React stores one on every DOM element it creates, and this doc walks it. Related:

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Easy