ESLint 9 Flat Config Patterns

Overview

ESLint 9 uses flat config (eslint.config.js) as the default. The legacy .eslintrc.* format is deprecated.

Key differences from .eslintrc:

• Single config file, explicit imports — no magic extends strings.
• Config is an exported array of config objects, applied in order.
• Plugins are imported directly, not referenced by string name.
• Glob patterns in files replace the old overrides system.

Basic Setup

JavaScript