React, Node.js & AI Tutorials

Node's built-in node:sqlite in TypeScript: the v26.11 Database rename, the transaction helper it lacks, the sync trade-off, and when better-sqlite3 wins.

Build an MCP server in TypeScript with the v2 SDK: registerTool with Zod schemas, stdio vs Streamable HTTP, stateless load balancing, and a v1-to-v2 diff table.

useActionState with real validation: typed Zod field errors, inputs that survive React 19's form reset, pending UI, and Vitest tests with real output.

How useEffect really works: the dependency array, cleanup functions, StrictMode double runs, async effects, and the cases where you should not use it.

useMemo caches a value, useCallback caches a function, React.memo skips a re-render. The difference, when each pays off, and what the React Compiler changes.

Use useRef for DOM nodes and mutable values that survive renders without triggering one. Covers useRef vs useState, ref callbacks, and TypeScript typing.

useReducer keeps related state in one place. Compare it with useState, type reducers with discriminated unions, and see where it beats a state library.

React Suspense shows a fallback while its children load. Covers React.lazy code splitting, boundary placement, streaming SSR, and avoiding layout flicker.

How React Server Components work in the Next.js App Router: the server and client boundary, data fetching, Server Actions, and the errors you will hit.

Take an LLM API from quickstart to production: server-side keys, SSE streaming, typed error handling, structured output, prompt caching, and timeouts.

Build a RAG pipeline end to end: chunking, embeddings, vector storage, reranking, and grounded prompts, plus how to evaluate retrieval instead of guessing.

Retrieval quality is set by chunking and search, not the prompt. Compares chunking strategies, text embeddings, hybrid search, reranking and measuring recall.

How tool calling actually works, writing tool descriptions models use correctly, capping the agent loop, keeping context small, and when not to build an agent.

Four ESP32 projects for beginners: set up the Arduino IDE, blink an LED, connect to Wi-Fi, read a DHT22 sensor, and run a web server, plus the pins to avoid.

Build a battery-powered ESP32 weather station: BME280 in forced mode, deep sleep between readings, static IP Wi-Fi, MQTT publishing, and battery monitoring.

How JWT auth actually works in Node.js: signing and verifying, access and refresh token rotation, where to store tokens, and when a session beats a JWT.

Design a REST API people can use: resource naming, the status codes that matter, error response shape, cursor pagination, and versioning without breakage.

Rate limit an API properly: fixed window vs sliding window vs token bucket, a Redis implementation, the RateLimit headers to send, and per-user keying.

Compare WebSockets, Server-Sent Events and polling for real-time data: reconnection, scaling across instances, proxy buffering, and which to actually pick.

Process files larger than memory with Node.js streams: readable and writable streams, pipeline, backpressure, async iterators, and the errors that leak memory.

Validate untrusted API input with Zod 4: schemas and inferred types, safeParse vs parse, discriminated unions, middleware, and what changed from Zod 3.

How React Context actually works: create a provider, read it with useContext, avoid the re-render trap, and know when Context beats Redux and when it loses.

Fetch data in React without the usual bugs: race conditions in useEffect, AbortController cleanup, and what SWR and TanStack Query actually cache for you.

Set up React with TypeScript in Vite, type props, state and events the React 19 way, and fix the compiler errors that code from older tutorials now triggers.

Tailwind CSS v4 breakpoints: the rem scale, max-* ranges, custom @theme breakpoints, using them in media queries, and when a container query fits better.

Compare React state management libraries: Zustand, Jotai, Recoil, Valtio, and Redux Toolkit. When to use each, plus useReducer and Context API trade-offs.

Poll APIs in React with TanStack Query: set up refetchInterval, add conditional polling and dynamic intervals, and avoid the common performance pitfalls.