Question 1

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 2

What are render props and how do they work?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes props and state. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The memoisation measurement in section 5 was produced by counting real renders on React 19.2.8. ## 1. Why This Even Matters — A Story First A weather station measures temperature. It has no opinion about whether you want a number, a dial, or a chart — so inst

Question 3

Explain the concept of 'composition' in React components.

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes props and components. **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 produced by actually counting renders on React 19.2.8 in this repo — this is the part of the answer that most candidates only assert. ## 1. Why This Even Matters — A Story First Consider two ways to build a range of co

Question 4

What are React custom hooks and when should you use them?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes useState and useEffect. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The state-independence result in section 3 was produced by mounting two components that use the same hook and clicking one of them on React 19.2.8. ## 1. Why This Even Matters — A Story First A recipe for bread is not a loaf o

Question 5

What are Higher-Order Components (HOCs) in React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes components and props. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The losses documented in section 4 were produced by actually building a naive HOC on React 19.2.8 and inspecting what survived. ## 1. Why This Even Matters — A Story First Think of a gift-wrapping service. You hand over a boxed appliance and get back the

REACT.JSDECODED.

Easy

What are React Components?

Medium

What are render props and how do they work?

Explain the concept of 'composition' in React components.

What are React custom hooks and when should you use them?

What are Higher-Order Components (HOCs) in React?