diff --git a/option.go b/option.go
new file mode 100644
index 0000000..b2414a7
--- /dev/null
+++ b/option.go
@@ -0,0 +1,10 @@
+package json
+
+type EncodeOption func(*Encoder) error
+
+func UnorderedMap() EncodeOption {
+	return func(e *Encoder) error {
+		e.unorderedMap = true
+		return nil
+	}
+}