This post goes over how to migrate ESLint from 8 to 9:

• Config
• Ignore
• Script
• Example

Config

Migrate the config:

npx @eslint/migrate-config .eslintrc.json

You may see the following:

Migrating .eslintrc.json

Wrote new config to ./eslint.config.mjs

You will need to install the following packages to use the new config:
- globals
- @eslint/js
- @eslint/eslintrc

You can install them using the following command:

npm install globals @eslint/js @eslint/eslintrc -D

Install the dependencies:

npm install globals @eslint/js @eslint/eslintrc -D

Delete the old config:

rm .eslintrc.json

Ignore

Install ESLint compatibility utilities:

npm install @eslint/compat -D

Update eslint.config.mjs:

import { includeIgnoreFile } from '@eslint/compat';
// ...

const gitignorePath = path.resolve(__dirname, '.gitignore');
// ...

export default [
  includeIgnoreFile(gitignorePath),
  // ...
];

To ignore a directory like dist:

// ...
export default [
  {
    ignores: ['dist/'],
  },
  // ...
];

Script

Run the script to ensure lint is working:

npx eslint .

Update package.json scripts (if applicable).

Example

• html-react-parser