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