# Reporting & Performance — ESLint + Prettier

Source: https://www.geekswithgeeks.com/en/eslint-prettier/eslint-prettier-18

> Optimize ESLint performance and generate useful reports.

## Performance tuning

ESLint can be slow on large codebases. Use --cache to skip unchanged files, and --max-warnings to treat warnings as errors when thresholds are exceeded.

## Performance optimization

Cache linting results and generate reports for visibility.

```bash
# Use cache for faster linting
eslint . --cache

# Generate JSON report
eslint . --format json > lint-report.json

# Package.json scripts
"scripts": {
  "lint": "eslint . --cache",
  "lint:report": "eslint . --format json > lint-report.json",
  "lint:html": "eslint . --format html > lint-report.html"
}
```

Output:

```
Cache and reporting configured
```

## Clear cache regularly

ESLint cache can become stale. Clear it with `rm .eslintcache` or `eslint . --cache --cache-location ./node_modules/.cache/eslint` before major updates.

Quick check

**Quiz:** What does the --cache flag do?

- [x] Caches linting results to skip unchanged files on next run.
- [ ] Stores config in memory.
- [ ] Increases memory usage.

*Answer:* Caches linting results to skip unchanged files on next run.. --cache significantly speeds up linting by skipping files that haven't changed since the last lint run.