Rabii Luena

An interactive learning guide for developers aiming to reach senior level with a frontend focus. Spanning 10 structured phases, it covers everything from JavaScript engine internals, TypeScript's advanced type system, and modern CSS layout — through React architecture, Next.js App Router, Node.js, databases, and real-time systems — all the way to testing strategies, security, observability, AI integration, and technical marketing.

App Router, strict TypeScript, ESLint + Prettier, a testing layer (Vitest/Jest + Playwright), and a clear separation between UI, domain logic, and infrastructure — the kind of structure a principal engineer would set up to keep the codebase scalable past the first few features.