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This page contains a high-level overview of some of the core concepts of ESLint.
ESLint is a configurable JavaScript linter. It's like spell check and autocorrect for your JavaScript code. It helps you write JavaScript in a consistent style and fix bugs in your code.
Rules are the core building block of ESLint. A rule validates if your code meets a certain expectation, and what to do if it does not meet that expectation. Rules can also contain additional configuration options specific to that rule.
For example, the semi rule lets you specify whether or not
JavaScript statements should end with a semicolon (;).
You can set the rule to either always require semicolons or require that
a statement never ends with a semicolon.
ESLint contains hundreds of built-in rules that you can use. You can also create custom rules or use rules that others have created with plugins.
For more information, refer to Rules.
An ESLint configuration file is a single place where you put all the configuration for ESLint your project. You can include built-in rules, how you want them enforced, plugins with custom rules, which files you want rules to apply to, and more.
For more information, refer to Configuration Files.
An ESLint plugin is an npm module that contains a set of ESLint rules. Plugins can be used to enforce a style guide and support JavaScript extensions (like TypeScript) or frameworks (like React). You can add single rules or sets of rules from a plugin. Often plugins come with recommended sets of rules that you can include in your project.
For more information, refer to Configuring Plugins.
An ESLint formatter controls the appearance of the linting results. If you're using a code editor with an ESLint integration to see linting results in line, the editor is using an ESLint formatter to display those results.
For more information, refer to Formatters.
One of the things that makes ESLint such a useful tool is the ecosystem of integrations that surrounds. These integrations extend the core functionality of ESLint. For example, many code editors have ESLint extensions that show you the ESLint results of your code in the file as you work so that you don't need to use the ESLint CLI to see linting results.
For more information, refer to Integrations. For a curated collection of popular ESLint integrations, see the awesome-eslint Github repository.
The ESLint CLI is a command line interface that lets you execute linting from the terminal. The CLI has a variety of options that you can pass to its commands.
The ESLint Node.js API lets you use ESLint programmatically from Node.js code. The API is useful when developing plugins, integrations, and other tools related to ESLint.
Unless you are extending ESLint in some way, you should use the CLI.
For more information, refer to Command Line Interface and Node.js API.