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Type React children as ReactNode, fix React.FC's missing children since React 18, and know when to use ReactElement, PropsWithChildren, or a render function.

Type a React onBlur handler as React.FocusEvent<HTMLInputElement>, pick the right element type, avoid the DOM FocusEvent, and use relatedTarget to track focus.

Next.js static export pages 404 on refresh because /about is saved as about.html. Fix it with trailingSlash: true or an nginx try_files rule on your own server.

Decode a JWT with jq or Node.js, read the header and claims, convert exp to a date, and see why decoding doesn't verify it or make it safe to paste online.

Add the Sentry MCP server to Claude Code with one command and a /mcp login, scope it to one project, or run it locally with a token for self-hosted Sentry.

Add the Playwright MCP server to Claude Code with one command, fix the 'chrome is not found' error, pass flags like --headless, and keep .playwright-mcp out of git.

Add the GitHub MCP server to Claude Code with one claude mcp add-json command, keep the PAT out of your config, and switch to read-only or specific toolsets.

Set up a Google Search Console API service account, grant it Restricted access, and wrap a searchAnalytics query script in a Claude Code skill, cloud included.

Change the default frontend and backend ports on Multica self-hosted so it stops clashing with other local projects on 3000 and 8080. No image rebuild needed.

Getting 'Cannot find native binding' for @tailwindcss/oxide in a pnpm workspace with Next.js Turbopack? Here's why it happens and how to fix it.

Use CLAUDE_CONFIG_DIR to run multiple Claude Code accounts with separate logins, hooks, skills, MCP servers, and CLAUDE.md files without touching ~/.claude.

Ignore personal files in one repo with .git/info/exclude instead of .gitignore. How it compares to .gitignore and core.excludesFile, and how to check with git.

Let Claude Code read your Datadog monitors, logs, metrics and APM. One claude mcp add command for the Datadog MCP server, OAuth login, and fixes for empty results.

Add the PagerDuty MCP server to Claude Code with one command: User API key, the archived local uvx server vs the hosted endpoint, EU accounts, write tools.

Trigger a React error boundary by throwing during render, testing the fallback in Jest, and using showBoundary for async or event-handler errors.

Fix `IntersectionObserver is not defined` in Jest by adding a clean global mock in `jest.setup.ts`. Includes TypeScript-safe setup and a test example.

Pass GitLab CI variables safely to Ansible shell tasks with extra-vars and task-level environment. Also explains why `export` in one task is not persisted.

Detect a click outside a modal or dropdown in React with Node.contains(), and close it by checking if the clicked element is a descendant.

Anonymous functions in useEffect show up as 'Anonymous function' in stack traces. Three ways to name your effect functions: a plugin, a rule, or a pattern.

TypeScript types event.target as EventTarget, which has no value. Use React.ChangeEvent<HTMLInputElement> or cast the target to HTMLInputElement.

useRef(null) types ref.current as null, so an if check narrows it to 'never'. Pass the element type with useRef<HTMLInputElement>(null), or JSDoc in .jsx.

jsdom in Jest has no window.matchMedia, so components that call it throw a TypeError. Add a matchMedia mock to your Jest setup file.

The z alias from zoxide doesnt work in non-interactive bash shells like cron jobs or tool subshells. Heres how to fix it with BASH_ENV.

Get a public HTTPS URL for localhost with one cloudflared quick tunnel command. No account needed. Handy for testing GitHub, Slack, or Stripe webhooks locally.

Set up wildcard subdomains with Caddy and DigitalOcean using DNS challenge. Build Caddy with the DigitalOcean DNS module and serve subdomains over HTTPS.

Fix CORS errors in json-server with a custom server.js and middleware. Covers preflight OPTIONS requests and when to use wildcard vs specific origin.

How to securely connect to a PostgreSQL database running inside a Docker container on a remote server, using an SSH tunnel — no open ports required.

Add Sequential Thinking MCP to Claude Code with one command, check that it is active with claude mcp list, and fix common setup errors.

Add Context7 MCP to Claude Code with one command, check that it is active with claude mcp list, and fix common install problems.

Discover 5 simple applications to enhance your JavaScript skills. Dive deeper into learning by trying out these JavaScript examples today!

Fix "Not implemented: window.scrollTo" (or "Window's scrollTo() method" in jsdom 27+) in Jest or Vitest by mocking window.scrollTo in your setup file.

Fix "ReferenceError: ResizeObserver is not defined" in Jest by mocking ResizeObserver in your setup file, so components that use it run in jsdom.

Make npm version create tags like 1.2.3 instead of v1.2.3 with tag-version-prefix. Covers project vs global config, CI release scripts, and a rollback.

Print GitLab CI environment variables for debugging with printenv, filter by prefix, and mask secrets so tokens never end up in job logs.

Test the Next.js Image component in Jest by mocking next/image as a plain img tag, then assert alt text and src. Includes a component test and common mistakes.

Test components that use next-i18next in Jest by mocking useTranslation so t() returns the key. Includes a component test and a global Jest setup file.

Fix Jest's 'Cannot use import statement outside a module' error with Swiper by letting transformIgnorePatterns transform it, or mock Swiper in unit tests.

Fix the Jest EMFILE too many open files error by lowering maxWorkers, ignoring build folders, raising ulimit, and running in band on CI.

Mock Next.js useRouter in Jest to control pathname and query and assert router.push, with a dynamic route example and the App Router next/navigation variant.

Fix the OpenSSL error digital envelope routines unsupported on Apple Silicon with the --openssl-legacy-provider flag, then upgrade your tooling.

Fix a feature branch based on the wrong parent with git rebase --onto, plus backup and force-with-lease checks that avoid losing work.

Fix the ENOSPC file watcher limit error on Linux when running Next.js, Vite, or Jest by raising the inotify limits, with commands to verify.

Run a Node.js project with nodemon and Babel: install @babel/node and preset-env, add a .babelrc, and add a start script that reruns modern JavaScript on save.

Keep only the Moment.js locales you need in Webpack with ContextReplacementPlugin, so the bundle stops shipping every locale, and check the size drop.

Find exactly where window.scrollTo is called in Jest tests using console.trace, jest.spyOn, and a few quick steps to narrow down the caller.