Question 1

What are the advantages of using React over plain JavaScript?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes JavaScript and DOM basics. **Difficulty:** Easy to Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. This is a trade-off question, so the answer below deliberately includes the costs — an interviewer is often testing whether you can argue against your own tool. ## 1. Why This Even Matters — A Story First Picture a whiteboard tracking a foot

Question 2

What is the Virtual DOM in React?

Accepted Answer

**Target Audience:** Anyone preparing for a React interview — assumes basic components. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The reconciliation behaviour in section 5 was produced by actually swapping an element type on React 19.2.8 and observing what happened to the child state. ## 1. Why This Even Matters — A Story First An architect wants three changes to a building. They do not de

Question 3

What is React and its main features?

Accepted Answer

**Target Audience:** Anyone preparing for a React interview — assumes no prior React knowledge. **Difficulty:** Easy > **How to read this doc:** Every concept is explained in plain language first. Right after, you will see a callout like 📌 Interview term: — the exact vocabulary an interviewer expects. The object-shape claims below were produced by running React 19.2.8 in this repo. ## 1. Why This Even Matters — A Story First Imagine decorating a room by giving instructions over

Question 4

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 5

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

REACT.JSDECODED.

Easy

What are the advantages of using React over plain JavaScript?

What is the Virtual DOM in React?

What is React and its main features?

Medium

What are React's design principles?

What is the difference between shadow DOM and virtual DOM?