The Notifications API allows web pages to control the display of system notifications to the end user — these are outside the top-level browsing context viewport, so therefore can be displayed even the user has switched tabs or moved to a different app. The API is designed to be compatible with existing notification systems across different platforms.
In the File System API, a FileException object represents error conditions that you might encounter while accessing the file system using the synchronous API. It extends the FileException interface described in File Writer and adds several new error codes.
The File and Directory Entries API simulates a local file system that web apps can navigate around. You can develop apps that can read, write, and create files and directories in a sandboxed, virtual file system.