JavaScript & TypeScript best practices

Apply these practices when writing or changing JavaScript/TypeScript. Prefer project conventions when they conflict; discover them first (tsconfig, oxlint/oxfmt, existing modules).

Defaults

1. Prefer TypeScript for new code when the project already uses it.
2. Match the project's module system ("type": "module", CJS, path aliases).
3. Prefer small, focused modules and functions with one clear job.
4. Prefer explicit types at boundaries (exports, public APIs, IO); let inference work inside function bodies.
5. Do not invent new style rules that fight the repo's formatter/linter.

TypeScript