The read-only fullPath property of the FileSystemEntry interface returns a string specifying the full, absolute path from the file system's root to the file represented by the entry.

This can also be thought of as a path which is relative to the root directory, with a "/" prepended to it to make it absolute.

A string indicating the entry's full path.

This example shows a function which is called with a file system; it then gets a FileSystemFileEntry for a file named data.json and returns its full path.

function gotFileSystem(fs) {
  let path = "";

  fs.root.getFile(
    "data.json",
    { create: true, exclusive: true },
    (entry) => {
      path = fullPath;
    },
    handleError(error),
  );

  return path;
}

Obviously, this is somewhat contrived, since we know that the file's full path is "/data.json", having just looked it up ourselves, but the concept holds up for scenarios in which you don't know it.

• File and Directory Entries API
• Introduction to the File and Directory Entries API
• FileSystemEntry