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eslint-plugin-baseline-js

Enforce the JavaScript Baseline (widely / newly / year) with a single ESLint rule powered by web‑features. This plugin delegates detection to eslint-plugin-es-x and ESLint core (plus a few small gap‑filling rules) and reports with one consistent Baseline message.

[![npm version][npm-version-src]][npm-version-href] [![npm downloads][npm-downloads-src]][npm-downloads-href] [![bundle][bundle-src]][bundle-href] [![JSDocs][jsdocs-src]][jsdocs-href] [![License][license-src]][license-href]

[!NOTE] This project hasn’t reached a major release yet, so behavior and options may change. Please feel free to report false negatives/positives and any rough edges as issues.

Install

• npm: npm i -D eslint-plugin-baseline-js • pnpm: pnpm add -D eslint-plugin-baseline-js • yarn: yarn add -D eslint-plugin-baseline-js

Recommended • ESLint >= 9.29.0 and

How It Works

1. Data → scripts/data/build-features.mjs • Extracts the minimal JavaScript subset from web‑features into src/baseline/data/features.javascript.ts. 2. Mapping → src/baseline/mapping/syntax.ts • Maps web‑features IDs to underlying rules (prefer eslint-plugin-es-x / ESLint core; custom rules only when necessary). 3. Resolution → src/baseline/resolve.ts • Classifies “beyond baseline” by bucket (high/low/false → widely/newly/limited) or year.

Coverage

We publish a generated coverage report that lists all JavaScript features from web‑features and shows which ones are currently mapped by this plugin.

• Report: docs/coverage.md • Regenerate locally: pnpm gen:coverage • Generator: scripts/coverage/generate-coverage.mjs

Options (rule)

| Option | Type | Default | Description |

| baseline | widely, newly, number, widely | Baseline level or year (alias: available). | | ignoreFeatures | string[] | — | Skip specific web‑features by ID (supports regex /.../) across syntax delegates and Web API/JS builtin detection. | | ignoreNodeTypes | string[] | — | Suppress reports by ESTree node.type (supports regex /.../). |

Use with oxlint

Runs as an oxlint JS plugin. Just drop it into .oxlintrc.json:

[!CAUTION] No type-aware detection under oxlint. Checks that need TypeScript type resolution (e.g., Set.difference(), Iterator.map()) won't fire. Use ESLint with the type-aware preset if you need them.

Baseline for HTML, CSS, and React

Baseline works best when HTML, CSS, JS, and React all align. For markup, styles, and React, enable the "use-baseline" rules from these ESLint plugins:

• ESLint for CSS: https://github.com/eslint/css • HTML ESLint (HTML): https://github.com/yeonjuan/html-eslint • HTML ESLint (React): https://github.com/yeonjuan/html-eslint/tree/main/packages/eslint-plugin-react

Branding Note (Baseline)

The Baseline name and logos are Google trademarks. Logo assets are licensed under CC BY‑ND 4.0. If you use Baseline logos alongside this plugin, please follow the official guidelines and do not imply sponsorship, affiliation, or endorsement by Google. We embed the official Baseline icons via their published URLs (unmodified).

License

MIT

Thanks to Anthropic for sponsoring

Description from the npm listing.