Client-Side Local Directory API Standards?

Working on a project where there is a need for a client to drag a local file-system Directory (Windows Explorer, MacOS Finder, etc) onto a Web Application in a current browser and for client-side JavaScript to iterate the files and directories within. Don't care if it's synchronous or asynchronous.

We have been looking at the Google/Mozilla FileSystem API and W3 File API standards but both, while functional and active in some browser versions, are either depreciated or dead standards. So my question is, what are the current accepted standard client-side JavaScript APIs for achieving this.

Requirements are simple: pure JavaScript, no browser extension. Current or emerging standards... anything.