ESLint

ESLint is the pluggable JavaScript linter: it statically analyzes code to find and automatically fix problems, ensuring consistency and preventing runtime bugs.

ESLint serves as the industry-standard, configurable linter for JavaScript and JSX, enforcing code quality and style across major organizations (e.g., Microsoft, Airbnb). It operates via static analysis, using the Espree parser to build an Abstract Syntax Tree (AST) and evaluate code against hundreds of built-in rules (e.g., `no-undef`, `prefer-const`). The tool’s core strength is its pluggability: every rule is a plugin, allowing developers to extend support for frameworks (React, Vue) or supersets (TypeScript via `@typescript-eslint/parser`). Crucially, the `--fix` command-line option can automatically resolve many issues, streamlining the development workflow and maintaining project standards.

https://eslint.org