Plugins are useful because your project may require some ESLint configuration that isn't included in the core `eslint` package. For example, if you're using a frontend JavaScript library like React or framework like Vue, these tools have some features that require custom rules outside the scope of the ESLint core rules.

For example, a popular shareable config is [eslint-config-airbnb](https://www.npmjs.com/package/eslint-config-airbnb), which contains a variety of rules in addition to some [parser options](../use/configure/language-options#specifying-parser-options). This is a set of rules for ESLint that is designed to match the style guide used by the [Airbnb JavaScript style guide](https://github.com/airbnb/javascript). By using the `eslint-config-airbnb` shareable config, you can automatically enforce the Airbnb style guide in your project without having to manually configure each rule.

To learn more about creating a shareable config, refer to [Share Configuration](shareable-configs).

For example, the custom formatter [eslint-formatter-gitlab](https://www.npmjs.com/package/eslint-formatter-gitlab) can be used to display ESLint results in GitLab code quality reports.

This class depends on the Node.js `fs` module and the file system, so you cannot use it in browsers. If you want to lint code on browsers, use the [Linter](#linter) class instead.

And here is an example of using the `ESLint` class with `lintText` API:

To enable flags in the VS Code ESLint Extension for the editor, specify the flags you'd like in the `eslint.options` setting in your `settings.json` file:

ESLint requires Node.js for installation. Follow the instructions in the [Getting Started Guide](getting-started) to install ESLint.

**Flat Config Mode Only.** This option runs `npx @eslint/config-inspector@latest` to start the config inspector. You can use the config inspector to better understand what your configuration is doing and which files it applies to. When you use this flag, the CLI does not perform linting.

The `content` strategy can be useful in cases where the modification time of your files changes even if their contents have not. For example, this can happen during git operations like `git clone` because git does not track file modification time.

This option runs `npm init @eslint/config` to start the config initialization wizard. It's designed to help new users quickly create an `.eslintrc` file by answering a few questions. When you use this flag, the CLI does not perform linting.

- `1`: Linting was successful and there is at least one linting error, or there are more linting warnings than allowed by the `--max-warnings` option.

If you are importing an object from another module, in most cases, you can just pass the object directly to the `defineConfig()` helper. For example, you can use the recommended rule configurations for JavaScript by importing the `recommended` config and using it in your array:

If you are importing an array from another module, pass the array directly to the `defineConfig()` helper. Here's an example:

**What To Do:** Run ESLint with the `--debug` command line flag and pass the file to check, like this:

**What To Do:** Run ESLint with the `--print-config` command line flag and pass the file to check, like this:

**What To Do:** Run ESLint with the `--inspect-config` command line flag and pass the file to check, like this:

You can also ignore files on the command line using `--ignore-pattern`, such as:

You can also unignore files on the command line using `--ignore-pattern`, such as:

1. When using `ignores` in an alternate configuration file specified using the `--config` command line option, glob patterns are evaluated relative to the current working directory.

1. When using `--ignore-pattern`, glob patterns are evaluated relative to the current working directory.

globalIgnores(["build/**/*"], "Ignore build directory"),

If you want to include patterns from a `.gitignore` file or any other file with gitignore-style patterns, you can use [`includeIgnoreFile`](https://github.com/eslint/rewrite/tree/main/packages/compat#including-ignore-files) utility from the [`@eslint/compat`](https://www.npmjs.com/package/@eslint/compat) package.

To remove the suppressions that are no longer needed, you can use the `--prune-suppressions` flag.

- [Legacy ESLint configuration files](../configure/configuration-files-deprecated#using-a-shareable-configuration-package) for documentation on the legacy ESLint configuration format

- [Configure Plugins](../configure/plugins) for documentation on how to extend from plugins

- [Create Plugins](../../extend/plugins#configs-in-plugins) for documentation on how to define plugins

You can specify a formatter using the `--format` or `-f` flag in the CLI. For example, `--format json` uses the `json` formatter.

Examples of each formatter were created from linting `fullOfProblems.js` using the `.eslintrc.json` configuration shown below.

`.eslintrc.json`:

```json

{

"extends": "eslint:recommended",

"rules": {

"consistent-return": 2,

"indent" : [1, 4],

"no-else-return" : 1,

"semi" : [1, "always"],

"space-unary-ops" : 2

}

}