fix

package.json

@@ -6,7 +6,8 @@
   "typings": "dist/index.d.ts",
   "scripts": {
     "lint": "eslint --fix .",
-    "build": "tsc"
+    "build": "tsc",
+    "test": "jest"
   },
   "repository": {
     "type": "git",

src/utility/utility.ts

@@ -2,10 +2,10 @@ export function isClass(target: any) {
   if (typeof target !== 'function') {
     return false;
   }
-  const proto = target.prototype;
-  return proto !== Function && proto !== Object;
+  const proto = target.constructor;
+  return proto === Function;
 }
 
 export function getClass(target: any): Function {
-  return isClass(target) ? target : target.constructor;
+  return isClass(target) ? target : getClass(target.constructor);
 }