The kind read-only property of the FileSystemHandle interface returns the type of entry. This is 'file' if the associated entry is a file or 'directory'. It is used to distinguish files from directories when iterating over the contents of a directory.

A string that can be:

• 'file': If the handle is a FileSystemFileHandle.
• 'directory': If the handle is a FileSystemDirectoryHandle.

The following function allows the user to choose a file from the file picker and then tests to see whether the handle returned is a file or directory

// store a reference to our file handle
let fileHandle;

async function getFile() {
  // open file picker
  [fileHandle] = await window.showOpenFilePicker();

  if (fileHandle.kind === "file") {
    // run file code
  } else if (fileHandle.kind === "directory") {
    // run directory code
  }
}

• File System API
• The File System Access API: simplifying access to local files