Add isArray

snippets/is-array.md

@@ -0,0 +1,9 @@
+### Is array
+
+Use `Array.isArray()` to check if a value is classified as an array.
+
+```js
+const isArray = val => val && Array.isArray(val);
+// isArray(null) -> false
+// isArray([1]) -> true
+```