Javascript

You can catch domain-specific anti-patterns that ESLint , Ruff , or golangci-lint miss by writing custom linter rules that parse your code into an Abstract Syntax Tree (AST), walk the tree to match specific node patterns, and report violations with auto-fix suggestions. The process is the same regardless of language: parse source into a tree, define the pattern you want to catch, walk the tree to find matches, and emit diagnostics. In JavaScript/TypeScript, this means writing an ESLint plugin with a visitor-pattern rule. In Python, you write a flake8 plugin using the ast module or a Ruff plugin in Rust. In Go, you use the go/ast and go/analysis packages.

Accessible web forms start with semantic HTML and use ARIA only to fill gaps native elements can’t reach. Use aria-live for error announcements and aria-describedby to link messages to fields. Following WCAG 2.2 AA ensures every user can perceive, navigate, and complete your forms using only a keyboard.

Most form accessibility failures are not caused by missing ARIA. They come from developers skipping basic HTML semantics like labels and fieldsets. Patching this damage with ARIA often makes things worse. The W3C’s first rule is simple: no ARIA is better than bad ARIA. Misapplied roles or redundant labels create noise instead of clarity.

Turborepo is a fast build system for JavaScript and TypeScript monorepos. It uses content-aware caching, parallel tasks, and smart dependency ordering. The result: multi-package repos that stay fast to work with. You define workspace packages in a pnpm-workspace.yaml file, then add a turbo.json that declares task dependencies and caching rules. Turborepo handles the rest. Running turbo run build only rebuilds packages whose source files changed. Cache hits restore build outputs in milliseconds instead of minutes.

Tailwind CSS v4 is a ground-up rewrite. The JavaScript-based PostCSS plugin is gone. In its place is a Rust-powered engine called Oxide. Configuration moves from tailwind.config.js into CSS-native @theme directives. Full builds run up to 5x faster, and incremental builds over 100x faster. The entry point is now a single @import "tailwindcss" line instead of three @tailwind directives. Most v3 projects can migrate in under an hour with the official @tailwindcss/upgrade codemod. Still, knowing what changed, and why, prevents surprises during the move.

A WebSocket chat needs two pieces. The server holds open connections and sends each message to every client. The browser client opens a socket, sends text on form submit, and shows new messages in the page. This build uses Node.js with the ws library and plain JavaScript on the client. No React, no Socket.IO, no build step. The whole thing fits in under 150 lines and handles dozens of users at once on a cheap server. This tutorial walks through every part.

Service workers give you a programmable network proxy right inside the browser. They sit between your page and the server, intercept every fetch request, and let you decide whether to serve a response from cache or from the network. For static sites - where every page is a pre-built file and every asset has a predictable URL - this is a natural fit. A well-configured service worker makes your static site load in single-digit milliseconds on repeat visits, work fully offline, and pass every Lighthouse PWA audit. The entire implementation fits in a single JavaScript file under 100 lines.