Update snippet, add extra tests

snippets/deepClone.md

@@ -6,23 +6,17 @@ tags: object,recursion,intermediate
 Creates a deep clone of an object.
 
 Use recursion.
+Check if the passed object is `null` and, if so, return `null`.
 Use `Object.assign()` and an empty object (`{}`) to create a shallow clone of the original.
 Use `Object.keys()` and `Array.prototype.forEach()` to determine which key-value pairs need to be deep cloned.
 
 ```js
 const deepClone = obj => {
-  let type = typeof obj;
-  let isAssignable = type === "function" || type === "object" && !!obj;
-  if (!isAssignable) {
-    return obj;
-  }
+  if (obj === null) return null;
   let clone = Object.assign({}, obj);
   Object.keys(clone).forEach(
     key => (clone[key] = typeof obj[key] === 'object' ? deepClone(obj[key]) : obj[key])
   );
-  if (obj) {
-    Object.setPrototypeOf(clone, Object.getPrototypeOf(obj));
-  }
   return Array.isArray(obj) && obj.length
     ? (clone.length = obj.length) && Array.from(clone)
     : Array.isArray(obj)