@jsenv/util/src/urlToExtension.js

Set of functions often needed when using Node.js.

import { urlToPathname } from "./urlToPathname.js"

export const urlToExtension = (url) => {
  const pathname = urlToPathname(url)
  return pathnameToExtension(pathname)
}

const pathnameToExtension = (pathname) => {
  const slashLastIndex = pathname.lastIndexOf("/")
  if (slashLastIndex !== -1) {
    pathname = pathname.slice(slashLastIndex + 1)
  }

  const dotLastIndex = pathname.lastIndexOf(".")
  if (dotLastIndex === -1) return ""
  // if (dotLastIndex === pathname.length - 1) return ""
  const extension = pathname.slice(dotLastIndex)
  return extension
}