1 files changed, 18 insertions, 0 deletions
diff --git a/std/node/_fs/_fs_common.ts b/std/node/_fs/_fs_common.ts
new file mode 100644
index 000000000..4de0899ea
--- /dev/null
+++ b/std/node/_fs/_fs_common.ts
@@ -0,0 +1,18 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+export interface FileOptions {
+  encoding?: string;
+  mode?: number;
+  flag?: string;
+}
+
+export function isFileOptions(
+  fileOptions: string | FileOptions | undefined
+): fileOptions is FileOptions {
+  if (!fileOptions) return false;
+
+  return (
+    (fileOptions as FileOptions).encoding != undefined ||
+    (fileOptions as FileOptions).flag != undefined ||
+    (fileOptions as FileOptions).mode != undefined
+  );
+}