javascript-idioms

JavaScript Idioms and Patterns

Modern JavaScript (ES2024+) rewards modules, async/await, and functional patterns. Idiomatic JS = strict mode, modular, well-tested.

Scope: Plain JavaScript only — projects with no tsconfig.json. This skill is intentionally thin: most JS guidance (coercion traps, async pitfalls, scope bugs, security, collections, performance) is shared with TypeScript and lives in one place to avoid divergence.

Loading guards:

• If tsconfig.json exists, do NOT load this skill — load @.agents/skills/typescript-idioms/SKILL.md instead. TypeScript is preferred whenever available.
• Coercion / async / scope / security / collection / performance pitfalls: see @.agents/skills/typescript-idioms/references/ts-patterns-and-anti-patterns.md — despite the filename, it is scoped to "TypeScript/JavaScript" and covers runtime pitfalls that apply to plain JS verbatim.
• Project layout: see @.agents/skills/typescript-idioms/references/project-structure.md (the generic backend/library/monorepo layouts are language-level, not TS-only).

Module System

1. ES modules over CommonJS for all new code:

   // ✅ ESM
   import { createTask } from './task-service.js';
   export function handler(req, res) { ... }