React Rendering and Reconciliation
React keeps a light picture of the UI in memory. When props or state change, React compares the new picture with the old one and updates only the parts that changed.
A teacher compares two answer sheets and only corrects the lines that changed instead of rewriting the whole page.
Topic practice prompts
Rendering calculates the next UI tree. Reconciliation compares previous and next trees and decides minimal DOM updates.
- What role do keys play?
- Can a component render without a DOM change?
Keys help React track identity between renders so it can reuse the right item and preserve state correctly.
- When is index acceptable?
- How can wrong keys break form state?
Last-day revision lines
- Render is calculation, not always DOM work.
- Commit is when the DOM changes.
- Parent renders can trigger child renders.
- Keys matter for lists with change.
- React interview questions ebook: context/React interview questions- Ebook.docx
- React questions PDF: context/ReactJS-Questions-and-answers.pdf
Local resource packs for this topic
Use these local packs when you want broader official-source context without leaving the app.
React Core Mental Models
A local digest of the React ideas that most often decide whether your answer sounds modern or outdated.
Rendering, state updates, re-renders, and explaining React without vague virtual-DOM-only answers.
Open local study packReact Effects and Data Flow
A local study pack for useEffect, shared state, and the difference between side effects and derived data.
Modern React interview rounds that test whether you overuse effects or design state carefully.
Open local study packRelated topics to study after this one
Hooks, Especially useEffect
Explain hooks clearly and use useEffect only for real side effects.
Simple mode, interview mode, example, pitfalls, and follow-ups are all inside this topic.
React Performance Toolkit
Measure first, then reduce render surface, expensive work, and bundle cost.
Simple mode, interview mode, example, pitfalls, and follow-ups are all inside this topic.