Use Set in filterNonUnique

snippets/filterNonUnique.md

@@ -5,11 +5,12 @@ tags: array,beginner
 
 Creates an array with the non-unique values filtered out.
 
+- Use `new Set()` and the spread operator (`...`) to create an array of the unique values in `arr`.
 - Use `Array.prototype.filter()` to create an array containing only the unique values.
 
 ```js
 const filterNonUnique = arr =>
-  arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));
+  [...new Set(arr)].filter(i => arr.indexOf(i) === arr.lastIndexOf(i));
 ```
 
 ```js