feat(posts): add "Migrate ESLint from 8 to 9"

Post: 2024-09-27-migrate-eslint-from-8-to-9.md

_posts/2024/2024-09-27-migrate-eslint-from-8-to-9.md

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+---
+layout: post
+title: Migrate ESLint from 8 to 9
+date: 2024-09-27 18:45:56
+excerpt: How to migrate ESLint from version 8 to 9.
+categories: eslint javascript
+---
+
+This post goes over how to [migrate ESLint from 8 to 9](https://eslint.org/docs/latest/use/configure/migration-guide):
+
+- [Config](#config)
+- [Ignore](#ignore)
+- [Script](#script)
+- [Example](#example)
+
+## Config
+
+Migrate the config:
+
+```sh
+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:
+
+```sh
+npm install globals @eslint/js @eslint/eslintrc -D
+```
+
+Delete the old config:
+
+```sh
+rm .eslintrc.json
+```
+
+## Ignore
+
+Install ESLint compatibility utilities:
+
+```sh
+npm install @eslint/compat -D
+```
+
+Update `eslint.config.mjs`:
+
+```js
+import { includeIgnoreFile } from '@eslint/compat';
+// ...
+
+const gitignorePath = path.resolve(__dirname, '.gitignore');
+// ...
+
+export default [
+  includeIgnoreFile(gitignorePath),
+  // ...
+];
+```
+
+To ignore a directory like `dist`:
+
+```js
+// ...
+export default [
+  {
+    ignores: ['dist/'],
+  },
+  // ...
+];
+```
+
+## Script
+
+Run the script to ensure lint is working:
+
+```sh
+npx eslint .
+```
+
+Update `package.json` scripts (if applicable).
+
+## Example
+
+- [html-react-parser](https://github.com/remarkablemark/html-react-parser/pull/1497/files)