linting-neostandard-eslint9

name: linting-neostandard-eslint9 description: Configures ESLint v9 flat config and neostandard for JavaScript and TypeScript projects, including migrating from legacy .eslintrc* files or the standard package. Use when you need to set up or fix linting with eslint.config.js or eslint.config.mjs, troubleshoot lint errors, configure neostandard rules, migrate from .eslintrc to flat config, or integrate linting into CI pipelines and pre-commit hooks. metadata: tags: linting, neostandard, eslint, eslint9, flat-config, javascript, typescript

When to use

Use this skill when you need to:

• Set up linting in a JavaScript or TypeScript project
• Use neostandard as a Standard-like ESLint v9 flat-config baseline
• Configure eslint@9 with the flat config system (eslint.config.js/eslint.config.mjs)
• Migrate from standard to neostandard or ESLint v9
• Migrate from legacy .eslintrc* configuration to ESLint v9
• Run linting consistently in CI and local development

Quick start: basic neostandard setup

Install dependencies and create a minimal eslint.config.js:

npm install --save-dev eslint@9 neostandard

// eslint.config.js
import neostandard from 'neostandard'

export default neostandard()

Verify the config works:

npx eslint .

Common setup workflow (new project)

1. Install eslint@9 and neostandard (see Quick start above)
2. Create eslint.config.js with neostandard() as the base
3. Add any project-specific rule overrides on top
4. Run npx eslint . to confirm no config errors
5. Add a lint script to package.json: "lint": "eslint ."
6. Integrate into CI with a non-fix run; use --fix only in local workflows

How to use

Read individual rule files for implementation details and examples:

• rules/neostandard.md - Install, configure, and extend neostandard with ESLint
• rules/eslint-v9-flat-config.md - Build ESLint v9 flat config for JS/TS projects
• rules/migration-from-standard.md - Migrate from standard to neostandard or ESLint v9
• rules/migration-from-legacy-eslint.md - Migrate from .eslintrc* to flat config safely
• rules/ci-and-editor-integration.md - CI scripts, pre-commit, and editor setup

Core principles

• Prefer reproducible linting with pinned major versions
• Keep config minimal and explicit
• Use flat config for ESLint v9 projects
• Treat lint failures as quality gates in CI
• Enable auto-fix for local workflows, but validate with non-fix CI runs