https://developer.chrome.com/docs/capabilities/web-apis/file-system-access


Using the File System Access API
To show off the power and usefulness of the File System Access API, I wrote a single file text editor. It lets you open a text file, edit it, save the changes back to disk, or start a new file and save the changes to disk. It's nothing fancy, but provides enough to help you understand the concepts.

https://googlechromelabs.github.io/text-editor/