Archive, multitagging, cleanup

Cleaned up the current snippets for consistency and minor problems, added multiple tags to most of them, archived a few.

snippets/isArray.md

@@ -5,10 +5,9 @@ Checks if the given argument is an array.
 Use `Array.isArray()` to check if a value is classified as an array.
 
 ```js
-const isArray = val => !!val && Array.isArray(val);
+const isArray = val => Array.isArray(val);
 ```
 
 ```js
-isArray(null); // false
 isArray([1]); // true
 ```