add toString() method to an enum

src/common/enums/crop-mode-persistence.enum.js

@@ -4,6 +4,23 @@ var CropModePersistence = Object.freeze({
   UntilPageReload: 1,
   CurrentSession: 2,
   Forever: 3,
+
+  toString: (cropModePersistence) => {
+    switch (cropModePersistence) {
+      case -1:
+        return 'default';
+      case 0:
+        return 'disabled';
+      case 1:
+        return 'until page reload';
+      case 2:
+        return 'current session';
+      case 3:
+        return 'forever';
+      default:
+        return 'unknown mode';
+    }
+  }
 });
 
 export default CropModePersistence;