eslint-plugin-escompat

ESLint plugin (v3.11.4) that reports errors for JavaScript/TypeScript syntax which, if left untranspiled, will not work in target browsers, as defined by a Browserslist config. Unlike eslint-plugin-compat (which checks for missing polyfills), this focuses on native syntax incompatibilities. It ships with recommended configs for browser code and separate TypeScript configs per ECMAScript target year. Integrates with both legacy .eslintrc and flat eslint.config.js formats. Actively maintained with multiple releases per year since initial release.