JavaScript Best Practices Skill

Agent Skills: JavaScript Best Practices

Idiomatic JavaScript patterns and conventions for maintainable code. Use when writing or refactoring JavaScript following idiomatic patterns and conventions. (triggers: **/*.js, **/*.mjs, module, import, export, error, validation)

UncategorizedID: hoangnguyen0403/agent-skills-standard/javascript-best-practices

JavaScript Best Practices

Priority: P1 (OPERATIONAL)

Conventions and patterns for writing maintainable JavaScript.

Implementation Guidelines

Naming: camelCase (vars/funcs), PascalCase (classes), UPPER_SNAKE (constants).
Errors: Throw Error objects only. Handle all async errors.
Comments: JSDoc for APIs. Explain "why" not "what".
Files: One entity per file. index.js for exports.
Modules: Named exports only. Order: Ext -> Int -> Rel.

Anti-Patterns

No Globals: Encapsulate state.
No Magic Numbers: Use const.
No Nesting: Guard clauses/early returns.
No Defaults: Use named exports.
No Side Effects: Keep functions pure.

Code

// Constants
const STATUS = { OK: 200, ERROR: 500 };

// Errors
class APIError extends Error {
  constructor(msg, code) {
    super(msg);
    this.code = code;
  }
}

// Async + JDoc
/** @throws {APIError} */
export async function getData(id) {
  if (!id) throw new APIError('Missing ID', 400);
  const res = await fetch(`/api/${id}`);
  if (!res.ok) throw new APIError('Failed', res.status);
  return res.json();
}

Reference & Examples

For module patterns and project structure: See references/REFERENCE.md.