update deepFreeze

snippets/deepFreeze.md

@@ -2,37 +2,23 @@
 
 Deep freezes an object.
 
-Calls `Object.freeze(obj)` recursively on all unfrozen properties of obj that are `typeof` function or object.
+Calls `Object.freeze(obj)` recursively on all unfrozen properties of passed object that are `instanceof` object.
 
 ```js
-const deepFreeze = obj => {
-  Object.freeze(obj);
-
-  Object.getOwnPropertyNames(obj).forEach(function(prop) {
-    if (
-      obj.hasOwnProperty(prop) &&
-      obj[prop] !== null &&
-      (typeof obj[prop] === 'object' || typeof obj[prop] === 'function') &&
-      !Object.isFrozen(obj[prop])
-    ) {
-      deepFreeze(obj[prop]);
-    }
-  });
-
-  return obj;
-};
+const deepFreeze = obj =>
+  Object.keys(obj).forEach(
+    prop =>
+      !obj[prop] instanceof Object || Object.isFrozen(obj[prop])
+        ? null
+        : deepFreeze(obj[prop])
+  ) || Object.freeze(obj);
 ```
 
 ```js
 'use strict';
 
-const a = Object.freeze([1, [2, 3]]);
+const o = deepFreeze([1, [2, 3]]);
 
-a[0] = 3; // not allowed
-a[1][0] = 4; // allowed but shouldn't be
-
-const b = deepFreeze([1, [2, 3]]);
-
-b[0] = 3; // not allowed
-b[1][0] = 4; // not allowed as well
+o[0] = 3; // not allowed
+o[1][0] = 4; // not allowed as well
 ```