diff --git a/client/MapJson.ts b/client/MapJson.ts
new file mode 100644
index 0000000..be64c19
--- /dev/null
+++ b/client/MapJson.ts
@@ -0,0 +1,20 @@
+// https://stackoverflow.com/questions/29085197/how-do-you-json-stringify-an-es6-map
+
+export default class MapJson {
+    static replacer(key: unknown, value: unknown) {
+        if (value instanceof Map) {
+            return {
+                dataType: 'Map',
+                value: Array.from(value.entries()), // or with spread: value: [...value]
+            }
+        } else {
+            return value
+        }
+    }
+    static reviver(key: unknown, value: any) {
+        if (value?.dataType === 'Map') {
+            return new Map(value.value)
+        }
+        return value
+    }
+}
\ No newline at end of file