Senior Frontend Depth

A blog series

Senior Frontend Depth: React Internals, TypeScript & Testing

Topics that come up most in interviews: how React really renders, hooks in depth, concurrent React and Server Components, how to manage state, advanced TypeScript, how to test, and accessibility.

Started 
2026
Lessons 
7
Reading 
~2 h

Contents

Every lesson has the same steps: what it is, how it works, a real example, common mistakes, then interview questions with answers you can say out loud.

  1. Lesson 00React Rendering Model: Render, Commit, Reconciliation and KeysWhat “render” really means, how React finds what changed between renders, why keys matter and how batching works.18 min
  2. Lesson 01Hooks in Depth: Effects, Refs and the RulesEffect dependencies, stale closures, useRef vs state, useLayoutEffect and the idea behind “You Might Not Need an Effect”.18 min
  3. Lesson 02Concurrent React, Suspense and Server Components in Next.jsTransitions, Suspense boundaries, streaming SSR, hydration errors and the line between server and client components.20 min
  4. Lesson 03State Management Decisions: Local, Context, Server Cache, Global StoreHow to sort state into kinds (UI, server, URL, form) and pick a tool for each kind, instead of arguing about libraries.15 min
  5. Lesson 04Advanced TypeScript for Interviews: Generics, Narrowing, Utility and Conditional TypesGeneric constraints, discriminated unions, infer, mapped types, satisfies, and keeping API response types correct from the server to the UI.20 min
  6. Lesson 05Frontend Testing Strategy: Unit, Integration, E2E and What to SkipTest what users see, not how the code is built. Mock the network, not your modules. Keep end-to-end tests for the key flows only.15 min
  7. Lesson 06Accessibility Essentials Interviewers CheckSemantic HTML first, focus in modals, ARIA only when needed, and testing with the keyboard.12 min

Glossary

37 terms used in this series. Inside any lesson, hover or tap a dotted term to see its meaning without leaving the page. Browse all terms →