The read-only isDirectory property of the FileSystemEntry interface is true if the entry represents a directory (meaning it's a FileSystemDirectoryEntry) and false if it's not.

You can also use isFile to determine if the entry is a file.

A Boolean indicating whether or not the FileSystemEntry is a directory.

This example shows how this property might be used to determine whether to process the entry as a directory or file. If the entry is neither, an error handler is called with an appropriate message.

if (entry.isDirectory) {
  processSubdirectory(entry);
} else if (entry.isFile) {
  processFile(entry);
} else {
  displayErrorMessage("Unsupported file system entry specified.");
}

• File and Directory Entries API
• Introduction to the File and Directory Entries API
• FileSystemEntry
• FileSystemEntry.isFile
• FileSystemDirectoryEntry