javascript-es2022

name	javascript-es2022
description	Use when implementing or refactoring JavaScript files (`.js`, `.mjs`, `.cjs`) in this repository. Applies Node.js 20+ ES2022 style, testing, and interaction rules from former `.github/instructions/javascript-es2022.instructions.md`.

JavaScript ES2022

Coding standards

• Use JavaScript with ES2022 features and Node.js (20+) ESM modules.
• Use Node.js built-in modules and avoid external dependencies where possible.
• Ask the user if additional dependencies are required before adding them.
• Always use async/await for asynchronous code, and use node:util promisify to avoid callbacks.
• Keep the code simple and maintainable.
• Use descriptive variable and function names.
• Do not add comments unless absolutely necessary; code should be self-explanatory.
• Never use null; always use undefined for optional values.
• Prefer functions over classes.

Naming and style

• Use PascalCase for classes, interfaces, enums, and type aliases; use camelCase for everything else.
• Exception: snake_case is permitted for DTOs, API contracts, and configuration files where external formats dictate it.
• Skip interface prefixes like I; rely on descriptive names.
• Name things for behavior or domain meaning, not implementation details.

Testing

• Use Vitest for testing.
• Write tests for all new features and bug fixes.
• Ensure tests cover edge cases and error handling.
• Never change production code to make it easier to test; test the real behavior.

Documentation

• When adding new features or making significant changes, update README.md where necessary.

User interactions

• Ask questions if implementation details or design choices are unclear.
• Always answer in the same language as the question, but keep generated code, comments, and docs in English.