---
name: javascript-tooling
description: Configure development tools, linting, formatting, and test runners for existing JavaScript projects. Use for ESLint, Prettier, Jest, or equivalent tool setup; defer application implementation and generic project scaffolding.
metadata:
  triggers:
    files:
    - '.eslintrc.*'
    - 'jest.config.*'
    - 'package.json'
    keywords:
    - eslint
    - prettier
    - jest
    - test
    - lint
    - build
---
# JavaScript Tooling

## **Priority: P1 (HIGH)**


## Implementation Guidelines

Start tooling recommendations with the applicable **Priority** and then state the formatting tool and enforcement point.

- **Linting**: ESLint (Rec + Prettier). Fix on save.
- **Formatting**: Prettier. Run on save/commit.
- **Testing**: Jest/Vitest. Co-locate tests. >80% cov.
- **Build**: Vite (Apps), Rollup (Libs).
- **Pkg Manager**: Sync versions (`npm`/`yarn`/`pnpm`).

## Anti-Patterns

- **No Formatting Wars**: Prettier rules.
- **No Untested Code**: TDD/Post-code tests.
- **No Dirty Commits**: Lint before push.

## Configuration

```javascript
// .eslintrc.js
module.exports = {
  extends: ['eslint:recommended', 'prettier'],
  rules: { 'no-console': 'warn', 'prefer-const': 'error' },
};
```

```json
// .prettierrc
{ "semi": true, "singleQuote": true, "printWidth": 80 }
```

```javascript
// jest.config.js
export default {
  coverageThreshold: { global: { lines: 80 } },
};
```

## Reference & Examples

For testing patterns and CI/CD:
See [references/REFERENCE.md](references/REFERENCE.md).

## Related Topics

best-practices | language

## Canonical response anchors

When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:
- Pkg Manager
- Priority
- Testing