javascript-pro

# JavaScript Pro ## When to Use This Skill - Building vanilla JavaScript applications - Implementing async/await patterns and Promise handling - Working with modern module systems (ESM/CJS) - Optimizing browser performance and memory usage - Developing Node.js backend services - Implementing Web Workers, Service Workers, or browser APIs ## Core Workflow 1. **Analyze requirements** — Review `package.json`, module system, Node version, browser targets; confirm `.js`/`.mjs`/`.cjs` conventions 2. **Design architecture** — Plan modules, async flows, and error handling strategies 3. **Implement** — Write ES2023+ code with proper patterns and optimisations 4. **Validate** — Run linter (`eslint --fix`); if linter fails, fix all reported issues and re-run before proceeding. Check for memory leaks with DevTools or `--inspect`, verify bundle size; if leaks are found, resolve them before continuing 5. **Test** — Write comprehensive tests with Jest achieving 85%+ coverage; if coverage falls short, add missing cases and re-run. Confirm no unhandled Promise rejections ## Reference Guide Load detailed guidance based on context: | Topic | Reference | Load When | |-------|-----------|-----------| | Modern Syntax | `references/modern-syntax.md` | ES2023+ features, optional chaining, private fields | | Async Patterns | `references/async-patterns.md` | Promises, async/await, error handling, event loop | | Modules | `references/modules.md` | ESM vs CJS, dynamic imports, package.json exports...