ESLint

ESLint is the standard linter for JS/TS. v9 (2024/2025) moved to Flat Config (eslint.config.js), a major breaking change that simplifies configuration.

When to Use

• Enforcing Rules: no-unused-vars, react-hooks/rules-of-hooks.
• Code Quality: Catching bugs before they run.

Core Concepts

Flat Config (eslint.config.js)

An array of objects. No more extends string hell.

export default [js.configs.recommended, { rules: { semi: "error" } }];