# Javascript > Best practices for JavaScript/TypeScript development including modern ES6+ patterns, error handling, and performance optimization. Use when this capability is needed. - Skill: `tomevault-io/javascript-2` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/javascript-2` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/javascript-2/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/javascript-2 --- # JavaScript/TypeScript Best Practices ## Code Style - Use const by default, let when reassignment is needed - Use template literals for string interpolation - Prefer arrow functions for callbacks - Use destructuring for object/array access - Use async/await over .then() chains - Use semicolons consistently (pick a style) ## Error Handling - Always handle promise rejections with .catch() or try/catch - Use try/catch with async/await - Provide meaningful error messages with context - Don't swallow errors silently - Create custom error classes for domain errors ## Modern Patterns - Use optional chaining (?.) and nullish coalescing (??) - Use spread operator for shallow object/array copies - Use Map/Set for complex data structures - Prefer for...of over forEach for iterables - Use Object.entries/keys/values for object iteration - Use Array.from() for array-like conversions ## TypeScript Specific - Prefer interfaces over type aliases for objects - Use strict mode in tsconfig.json - Avoid 'any' type - use 'unknown' if needed - Use generics for reusable type-safe code - Use discriminated unions for type narrowing - Leverage const assertions for literal types ## Performance - Avoid creating functions inside loops - Use object pools for frequent allocations - Debounce/throttle expensive operations - Use Web Workers for CPU-intensive tasks --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/kprsnt2) — claim your Tome and manage your conversions.