The JavaScript support is just as good as the TypeScript support, because TypeScript loves JavaScript. The best way to use in a JavaScript project is to create a tsconfig.json with allowJs set to true:

{
  "compilerOptions": {
    "allowJs": true,
    "outDir": "./dist"
  }
}

Note: outDir is required with allowJs because you don't want to overwrite your JS source by mistake 🌹.