Question 1

What is JSX?

Accepted Answer

**Target Audience:** Anyone preparing for a React interview — assumes JavaScript basics, no React required. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The compiled output in section 3 was produced by actually running a JSX source file through this project bundler toolchain, and the escaping behaviour in section 5 by rendering it in React 19.2.8. ## 1. Why This Even Matters — A Story First M

Question 2

What are fragments in React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes basic JSX. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The DOM output in section 3 was produced by rendering both versions in React 19.2.8 and reading back the real HTML. ## 1. Why This Even Matters — A Story First You need to post three documents. The post office insists on one item, so you put them in an envelope. Fine

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 is the role of a bundler like Webpack in a React project?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes you have run a build. **Difficulty:** Easy to Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The compiled output in section 3 was produced by running a real JSX file through this project own compiler toolchain, not copied from documentation. ## 1. Why This Even Matters — A Story First A publisher does not hand a reader a box of loose man

Question 5

How do you handle routing in React applications?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — no prior routing knowledge assumed. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** no client router is installed in this repo — routing here is Next.js's file-based App Router (**16.3.4** installed) — so no router API was executed. The **data-loading measurements** the argument turns on were executed and

Question 6

What are Server Actions and the `"use server"` directive in React 19?

Accepted Answer

**Target Audience:** Engineers preparing for senior React interviews — assumes Actions. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** the directive is a bundler-plus-runtime feature and this repo has **no RSC runtime**, so the server half was not executed. The **client half was** — a plain

Question 7

What changed with Context in React 19 (`<Context>` as a provider)?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes the Context API. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every claim below — including whether the old syntax still works and what Context.Provider now *is* — was produced by running the code on React 19.2.8 rather than read from a changelog. ## 1. Why This Even Matters — A Story First For years you addr

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