best-practices
Apply modern web development best practices for security, compatibility, and code quality. Use when asked to "apply best practices", "security audit", "modernize code", "code quality review", or "check for vulnerabilities".
DeepseekModel
キュレーション済みスキル
品質 優秀 · 90
v1.0.0
取得
https://deepseekmodel.com/api/download.php?id=addyosmani-web-quality-skills-skills-best-practices-skill-md&format=skill
ダウンロード .skill
標準形式。system_prompt と model_config を収録し、任意の Agent で利用可能
.skill ファイルの system_prompt フィールドの実際の内容。
name best-practices description Apply modern web development best practices for security, compatibility, and code quality. Use when asked to "apply best practices", "security audit", "modernize code", "code quality review", or "check for vulnerabilities". license MIT metadata {"author":"web-quality-skills","version":"2.0"} Best practices Modern web development standards based on Lighthouse best practices audits. Covers security, browser compatibility, and code quality patterns. Evidence-led audit workflow When a rendered page is available: Run a live Lighthouse Best Practices audit when that capability is available; with Chrome DevTools MCP, use lighthouse_audit . Use navigation mode for a normal page load or snapshot mode when the current state must be preserved. Inspect the listed console and network failures and fetch individual details only when they support a finding. Supplement runtime evidence with dependency, header, configuration, and source inspection; Lighthouse is not a complete security assessment. Fix the implicated code, re-run the same audit, and keep security findings separate from style preferences. If live tools are unavailable, use the Lighthouse CLI plus focused dependency and header checks. Never report a high Lighthouse score as proof that the application is secure. Security Read the security reference when security is in scope or a live audit surfaces a related failure. It covers HTTPS/HSTS, CSP and Trusted Types, Subresource Integrity, headers, dependencies, sanitization, and cookies. At minimum: Use HTTPS without mixed content. Add HSTS only after confirming every relevant subdomain supports HTTPS. Treat a strict CSP as defense in depth. Prefer nonces or hashes and test with report-only before enforcement. Sanitize untrusted HTML and protect DOM XSS sinks. Prefer text APIs when markup is not required. Pin and review third-party code. Use SRI where the delivery model supports it and keep dependencies patched. Verify response headers at runtime. Source configuration alone does not prove what the deployed page sends. Browser compatibility Doctype declaration <!-- ❌ Missing or invalid doctype --> < HTML > <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" > <!-- ✅ HTML5 doctype --> <!DOCTYPE html > < html lang = "en" > Character encoding <!-- ❌ Missing or late charset --> < html > < head > < title > Page </ title > < meta charset = "UTF-8" > </ head > <!-- ✅ Charset as first element in head --> < html > < head > < meta charset = "UTF-8" > < title > Page </ title > </ head > Viewport meta tag <!-- ❌ Missing viewport --> < head > < title > Page </ title > </ head > <!-- ✅ Responsive viewport --> < head > < meta charset = "UTF-8" > < meta name = "viewport" content = "width=device-width, initial-scale=1" > < title > Page </ title > </ head > Feature detection // ❌ Browser detection (brittle) if (navigator. userAgent . includes ( 'Chrome' )) { // Chrome-specific code } // ✅ Feature detection if ( 'IntersectionObserver' in window ) { // Use IntersectionObserver } else { // Fallback } // ✅ Using @supports in CSS @ supports ( display : grid) { . container { display : grid; } } @supports not ( display : grid) { . container { display : flex; } } Polyfills (when needed) Prefer bundling polyfills at build time (Babel/SWC + core-js , or @vitejs/plugin-legacy ) targeted by your supported-browsers list. This eliminates the runtime check entirely and avoids shipping polyfill bytes to modern browsers. If you must load a polyfill at runtime, append a script element — never use document.write (it blocks the parser and is broken in async/deferred contexts): < script > if (!( 'fetch' in window )) { const s = document . createElement ( 'script' ); s. src = '/polyfills/fetch.js' ; s. defer = true ; document . head . appendChild (s); } </ script > Never load polyfills from a third-party CDN you don't control. The polyfill.io service was compromised in mid-2024 in a supply-chain attack and used to serve malware to ~100k sites. Self-host, or use a vetted mirror (e.g. Cloudflare's cdnjs polyfill build ) — and pin the version with Subresource Integrity . Deprecated APIs Avoid these // ❌ document.write (blocks parsing) document . write ( '<script src="..."></script>' ); // ✅ Dynamic script loading const script = document . createElement ( 'script' ); script. src = '...' ; document . head . appendChild (script); // ❌ Synchronous XHR (blocks main thread) const xhr = new XMLHttpRequest (); xhr. open ( 'GET' , url, false ); // false = synchronous // ✅ Async fetch const response = await fetch (url); // ❌ Application Cache (deprecated) < html manifest = "cache.manifest" > // ✅ Service Workers if ('serviceWorker' in navigator) { navigator.serviceWorker.register('/sw.js'); } Event listener passive // ❌ Non-passive touch/wheel (may block scrolling) element. addEventListener ( 'touchstart' , handler); element. addEventListener ( 'wheel' , handler); // ✅ Passive listeners (allows smooth scrolling) element. addEventListener ( 'touchstart' , handler, { passive : true }); element. addEventListener ( 'wheel' , handler, { passive : true }); // ✅ If you need preventDefault, be explicit element. addEventListener ( 'touchstart' , handler, { passive : false }); Console & errors No console errors // ❌ Errors in production console . log ( 'Debug info' ); // Remove in production throw new Error ( 'Unhandled' ); // Catch all errors // ✅ Proper error handling try { riskyOperation (); } catch (error) { // Log to error tracking service errorTracker. captureException (error); // Show user-friendly message showErrorMessage ( 'Something went wrong. Please try again.' ); } Error boundaries (React) class ErrorBoundary extends React.Component { state = { hasError : false }; static getDerivedStateFromError ( error ) { return { hasError : true }; } componentDidCatch ( error, info ) { errorTracker. captureException (error, { extra : info }); } render ( ) { if ( this . state . hasError ) { return < FallbackUI /> ; } return this . props . children ; } } // Usage < ErrorBoundary > < App /> </ ErrorBoundary > Global error handler // Catch unhandled errors window . addEventListener ( 'error' , ( event ) => { errorTracker. captureException (event. error ); }); // Catch unhandled promise rejections window . addEventListener ( 'unhandledrejection' , ( event ) => { errorTracker. captureException (event. reason ); }); Source maps Production configuration // ❌ Source maps exposed in production // webpack.config.js module . exports = { devtool : 'source-map' , // Exposes source code }; // ✅ Hidden source maps (uploaded to error tracker) module . exports = { devtool : 'hidden-source-map' , }; // ✅ Or no source maps in production module . exports = { devtool : process. env . NODE_ENV === 'production' ? false : 'source-map' , }; Strip sourcesContent from production maps when uploading to your error tracker. By default, bundlers embed the full original source inside the .map file — anyone who obtains the map (including via a misconfigured upload step) gets your unminified code. Configure your bundler to omit sourcesContent , or use a Sentry/Bugsnag CLI flag that does so when uploading. For Vite, prefer sourcemap: 'hidden' over 'true' so the //# sourceMappingURL= comment isn't emitted into the bundle. Performance best practices Avoid blocking patterns // ❌ Blocking script <script src= "heavy-library.js" ></script> // ✅ Deferred script < script defer src = "heavy-library.js" > </ script > // ❌ Blocking CSS import @ import url ( 'other-styles.css' ); // ✅ Link tags (parallel loading) <link rel="stylesheet" href="styles.css"> <link rel="stylesheet" href="other-styles.css"> Efficient event handlers // ❌ Handler on every element items. forEach ( item => { item. addEventListener ( 'click' , handleClick); }); // ✅ Event delegation container. addEventListener ( 'click' , ( e ) => { if (e. target . matches ( '.item' )) { handleClick (e); } }); Memory management // ❌ Memory leak (never removed) const handler = ( ) => { /* ... */ }; window . addEventListener ( 'resize' , handler); // ✅ Cleanup when done const handler = ( ) => { /* ... */ }; window . addEventListener ( 'resize' , handler); // Later, when component unmounts: window . removeEventListener ( 'resize' , handler); // ✅ Using AbortController const controller = new AbortController (); window . addEventListener ( 'resize' , handler, { signal : controller. signal }); // Cleanup: controller. abort (); Code quality Valid HTML <!-- ❌ Invalid HTML --> < div id = "header" > < div id = "header" > <!-- Duplicate ID --> < ul > < div > Item </ div > <!-- Invalid child --> </ ul > < a href = "/" > < button > Click </ button > </ a > <!-- Invalid nesting --> <!-- ✅ Valid HTML --> < header id = "site-header" > </ header > < ul > < li > Item </ li > </ ul > < a href = "/" class = "button" > Click </ a > Semantic HTML <!-- ❌ Non-semantic --> < div class = "header" > < div class = "nav" > < div class = "nav-item" > Home </ div > </ div > </ div > < div class = "main" > < div class = "article" > < div class = "title" > Headline </ div > </ div > </ div > <!-- ✅ Semantic HTML5 --> < header > < nav > < a href = "/" > Home </ a > </ nav > </ header > < main > < article > < h1 > Headline </ h1 > </ article > </ main > Image aspect ratios <!-- ❌ Distorted images --> < img src = "photo.jpg" width = "300" height = "100" > <!-- If actual ratio is 4:3, this squishes the image --> <!-- ✅ Preserve aspect ratio --> < img src = "photo.jpg" width = "300" height = "225" > <!-- Actual 4:3 dimensions --> <!-- ✅ CSS object-fit for flexibility --> < img src = "photo.jpg" style = "width: 300px; height: 200px; object-fit: cover;" > Permissions & privacy Request permissions properly // ❌ Request on page load (bad UX, often denied) navigator. geolocation . getCurrentPosition (success, error); // ✅ Request in context, after user action findNearbyButton. addEventListener ( 'click' , async () => { // Explain why you need it if ( await showPermissionExplanation ()) { navigator. geolocation . getCurrentPosition (success, error); } }); Permissions policy <!-- Restrict powerful features --> < meta http-equiv = "Permissions-Policy" content = "geolocation=(), camera=(), microphone=()" > <!-- Or allow for specific origins --> < meta http-equiv = "Permissions-Policy" content = "geolocation=(self 'https://maps.example.com')" >
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ダウンロードした .skill に含まれるフィールド。
| フィールド | 説明 |
|---|---|
| format | フォーマット識別子（skill/v1） |
| skill_id | スキル固有 ID |
| name | スキル名 |
| version | バージョン |
| description | 説明 |
| category | カテゴリ（配列） |
| trigger_words | トリガーワード |
| tags | タグ |
| source | ソース |
| source_url | ソース URL（本ページ） |
| exported_at | エクスポート日時（ダウンロード毎） |
| system_prompt | システムプロンプト本文 |
| model_config | モデル設定：provider / model / temperature / max_tokens / top_p |
| examples | サンプル |
| install_guide | 各プラットフォームの導入説明（Coze / Dify / Claude / カスタム） |
