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

You can also use isDirectory to determine if the entry is a directory.

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

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.isDirectory
• FileSystemFileEntry