Gio.OutputStream.prototype.flush_async

function flush_async(io_priority: Number(gint), cancellable: Gio.Cancellable, callback: Gio.AsyncReadyCallback): void {
    // Gjs wrapper for g_output_stream_flush_async()
}
  

Forces an asynchronous write of all user-space buffered data for the given stream. For behaviour details see Gio.OutputStream.prototype.flush.

When the operation is finished callback will be called. You can then call Gio.OutputStream.prototype.flush_finish to get the result of the operation.