ESLint

ESLint is a static code analysis tool for identifying problematic patterns in JavaScript code and for enforcing coding style. It analyzes source code to flag potential bugs, anti-patterns, and stylistic inconsistencies. The project is open source and extensible through plugins and custom rules. ESLint supports JavaScript and TypeScript via additional parsers, and can be configured to target different environments and runtimes.

ESLint uses Espree as its default JavaScript parser and builds an abstract syntax tree to apply rules. Its architecture is modular: core rules are complemented by plugins that provide extra rules and configurations. Rules can be configured with severities such as off, warn, or error, and many can be automatically fixed with the --fix option. Configuration is stored in files such as .eslintrc.json or .eslintrc.js, using fields like extends, plugins, parser, parserOptions, and rules. Projects commonly extend recommended configurations and combine ESLint with other tools to maintain code quality and consistency.

ESLint has a large ecosystem of plugins and shareable configurations, including plugins for React, TypeScript, Node, and import/export syntax, as well as configurations such as airbnb, google, and standard. It is integrated into editors, build tools, and continuous integration pipelines, and is typically invoked via npm scripts or task runners. ESLint is published under the MIT License and is maintained by a broad community of contributors.