method FileHandle.appendFileFileHandle.appendFile(data: string | Uint8Array,options?: (ObjectEncodingOptions & FlagAndOpenMode & { flush?: boolean | undefined; }) | BufferEncoding | null,): Promise<void>Alias of filehandle.writeFile(). When operating on file handles, the mode cannot be changed from what it was set to with fsPromises.open(). Therefore, this is equivalent to filehandle.writeFile(). Parametersdata: string | Uint8Arrayoptionaloptions: (ObjectEncodingOptions & FlagAndOpenMode & { flush?: boolean | undefined; }) | BufferEncoding | nullReturn TypePromise<void>Fulfills with undefined upon success.